Patent Application
20100281897
The present invention relates to a motor current calculation device. The present invention also relates to an air conditioning apparatus comprising the motor current calculation device.
An air conditioning apparatus comprises a compressor, a variety of devices such a compressor, a fan and the like. A motor is often used as a power source for these devices. The motor is connected to a motor drive unit (called a “driver” below) composed of a plurality of switching elements, and can be caused to rotate using a drive voltage outputted by turning the switching elements in the driver ON and OFF.
In some cases, the rotational speed of the motor is controlled in order to operate the various types of devices such as the compressor, the fan in an appropriate state. A motor current that is passed through the motor is often used for such motor rotational speed control.
Here, as a method for detecting the motor current, for example, as disclosed in Patent Document 1, there is known a technology where shunt resistor used as current-detecting elements are serially connected to the wiring through which the motor current flows, and the motor current is detected based on the voltages at either end of the shunt resistor.
<Patent Document 1>Japanese Laid-open Patent Application No. 2005-192358
Other than when the motor and the driver are separately disposed, sometimes the motor and the driver are built into a motor device. However, in such a motor device, when the technique pertaining to Patent Document 1 is applied to detect motor current flowing in the motor portion, in terms of the configuration of the motor device, the drive current flowing through the driver ends up flowing in addition to the motor current on the wire where the shunt resistor is connected in series, so obtaining the motor current only ends up becoming difficult.
An object of the present invention is to provide a motor current calculation device enabling the motor current to be readily found, and an air conditioning apparatus comprising the motor current calculation device.
A motor current calculation device according to a first aspect of the present invention comprises a first wire, a current detecting unit, a decision unit, and a calculation unit. A motor current that has been passed through a motor and a drive current that has been passed through a motor drive unit for driving the motor flow through the first wire. The current detecting unit detects the sum of the motor current and the drive current flowing through the first wire. The decision unit determines a detection result of the current detecting unit when the motor is not rotating as the drive current. The calculation unit calculates the motor current by subtracting the drive current determined by the decision unit from a detection result of the current detecting unit when the motor is rotating.
When the motor is not rotating (i.e., when the motor is making approximately zero rotations per minute), the motor current is substantially 0 A; however, since the drive current flows through the motor drive unit, the current detecting unit is capable of detecting the drive current. Therefore, the motor current calculation device calculates the motor current by subtracting the detection result of the current detecting unit when the motor is not rotating from a detection result of the current detecting unit when the motor is rotating. It is thereby possible to determine the motor current in a simple manner, even when both the motor current and the drive current flow through the first wire. Moreover, since the detection result of the current detector when the motor is not rotating is used in the calculations, then if the calculation unit comprises, e.g., a microcomputer, the capacity of the microcomputer can be reduced.
A motor current calculation device according to a second aspect of the present invention comprises the motor current calculation device according to the first aspect of the present invention, further comprising a current leveling unit. The current leveling unit levels the drive current before the drive current has flowed through the first wire.
Since the motor current and the leveled drive current flow through the first wire, the current detecting unit can detect the sum of the motor current and the leveled drive current. Consequently, the calculation unit can determine the motor current using stable detection results that include the drive current.
A motor current calculation device according to a third aspect comprises is the motor current calculation device according to the second aspect of the present invention, further comprising a second wire. The drive current flows through the second wire. The current leveling unit has a resistor and a capacitor. The resistor is connected in series on the second wire. The capacitor is connected to the second wire in parallel with respect to the resistor.
The current leveling unit in the motor current calculation device is configured by a so-called filter circuit comprising the resistor and the capacitor. The motor current calculation device can level the drive current with the current leveling unit having a simple configuration.
A motor current calculation device according to a fourth aspect of the present invention comprises the motor current calculation device of any of the first through third aspects of the present invention, wherein the motor and the motor drive unit are included in a motor device.
When the motor and the motor drive unit are built into the motor device, in terms of the consideration thereof, it is difficult to separately dispose the wire on which the motor current that has been passed through the motor flows and the wire on which the drive current that has been passed through the motor drive unit flows. However, when the motor current calculation device according to the present invention is used in such a case, the detection results of the current detecting unit when the motor is not operating are used in calculations as the drive current; therefore, the motor current calculation device can calculate the motor current very accurately.
An air conditioning apparatus according to a fifth aspect of the present invention comprises a motor current calculation device, a fan motor, a fan, and a control unit. The motor current calculation device is the motor current calculation device according to any of the first through fourth aspects of the present invention. The fan motor is included in the motor device together with the motor drive unit, and motor current is passed through the fan motor. The fan is driven to rotate by the fan motor. The control unit performs control of the volume of air sent into a room from the fan on the basis of the motor current that has been calculated by the calculation unit of the motor current calculation device.
According to this air conditioning apparatus, it is possible to perform a control based on the accurate motor current calculated by the motor current calculation device so that, e.g., the volume of air sent into a room remains constant.
According to the motor current calculation device of the first aspect of the present invention, it is possible to determine the motor current in a simple manner, even when both the motor current and the drive current flow through the first wire. Moreover, since the detection result of the current detector when the motor is not rotating is used in the calculations, then if the calculation unit comprises, e.g., a microcomputer, the capacity of the microcomputer can be reduced.
According to the motor current calculation device of the second aspect of the present invention, the calculation unit can determine the motor current using stable detection results that include the drive current.
According to the motor current calculation device of the third aspect of the present invention, the drive current is leveled using the current leveling unit having a simple configuration.
According to the motor current calculation device of the fourth aspect of the present invention, even if the motor and the motor drive unit are built into the motor device, the detection results when the motor is not rotating are used in calculations as the drive current; therefore, the motor current calculation device can calculate the motor current very accurately.
According to the air conditioning apparatus of the fifth aspect of the present invention, it is possible to perform a control based on the accurate motor current calculated by the motor current calculation device so that, e.g., the volume of air sent into a room remains constant.
The following is a description, made with reference to the drawings, of a motor current calculation device according to the present invention and an air conditioning apparatus comprising this motor current calculation device.
(1) Configuration
This type of air conditioning apparatus 1 comprises mainly a casing 2, first and second heat exchangers 3a, 3b, a compressor 4, a compressor motor 5, first and second fans 6a, 6b, a first fan motor 7, a second fan motor device 8, a motor current calculation device 9, and a control unit 11, as shown in
(1-1) Casing
The casing 2 has a substantially rectangular parallelepiped shape, inside of which are housed the first and second heat exchangers 3a, 3b, the compressor 4, the first and second fans 6a, 6b, and other components. In
A partitioning plate 26 for partitioning the interior of the casing 2 is provided inside the casing 2. The interior of the casing 2 is divided by this partitioning plate 26 into an air chamber S1 and a machine chamber S2. The first and second heat exchangers 3a, 3b and the partitioning member between the heat exchangers 3a, 3b are disposed in the air chamber S1; and the other devices excluding the first and second heat exchangers 3a, 3b (i.e., the compressor 4, the first and second fans 6a, 6b, etc.) are disposed in the machine chamber S2.
(1-2) Heat Exchangers The first heat exchanger 3a and the second heat exchanger 3b are cross-fin type fin-and-tube heat exchangers, comprising numerous aluminum fins 31 formed into a substantially rectangular plate shapes, and copper heat transfer tubes 32 passing through the fins 31, as shown in
These first and second heat exchangers 3a, 3b are connected to each other via an expansion valve 13 as shown in
The first and second heat exchangers 3a, 3b described above are controlled by the control unit 11 so as to enable a first state in which the first heat exchanger 3a functions as a condenser and the second heat exchanger 3b functions as an evaporator, or a second state in which the first heat exchanger 3a functions as an evaporator and the second heat exchanger 3b functions as a condenser. In the first state, an adsorptive agent reproducing action is performed for removing moisture from the adsorptive agent when the first heat exchanger 3a functions as a condenser, and an adsorption action is performed for causing moisture to absorb to the adsorptive agent when the second heat exchanger 3b functions as an evaporator. In the second state, an adsorption action is performed for causing moisture to absorb to the adsorptive agent when the first heat exchanger 3a functions as an evaporator, and an adsorptive agent reproducing action is performed for removing moisture from the adsorptive agent when the second heat exchanger 3b functions as a condenser. By alternatively performing the adsorption action and the reproducing action in this maenner and switching the flow channels of the air EA, SA supplied in and out of the room through the heat exchangers 3a, 3b, the moisture in the adsorptive agent can be continually adsorbed and emitted (i.e., removed). Consequently, the air conditioning apparatus 1 can perform variety operations while maintaining dehumidification performance or humidification performance.
The flow channels of the air EA, SA supplied in and out of the room through the heat exchangers 3a, 3b are switched by a switching damper (not shown). The switching damper switches the flow channels of the air so that the outdoor air OA or room air RA are blown out from the first blowout opening 24 or the second blowout opening 25 after passing through either of the first heat exchanger 3a or the second heat exchanger 3b.
(1-3) Compressor and Compressor-Use Motor
The compressor 4 is connected to the first heat exchanger 3a and the second heat exchanger 3b via a four-way switching valve 12, as shown in
The compressor-use motor 5 is connected to the compressor 4. The compressor-use motor 5 is, a brushless DC motor, for example, and is driven to rotate by a driver 51 (
(1-4) Fan and Fan Motor
The first fan 6a is disposed in a position corresponding to the first blowout opening 24, and the exhaust air EA is blown outside of the casing 2 (specifically, the outdoors) via the first blowout opening 24, as shown in
The first fan motor 7 is connected to the first fan 6a. Like the compressor-use motor 5, the first fan motor 7 is a brushless DC motor for example; and is controlled to rotate by a first motor driver 71 for the first fan motor 7. The second fan motor device 8 is connected to the second fan 6b, and is a device including a second fan motor 81 and a second motor driver 82 (equivalent to a motor drive unit), as shown in
(1-5) Motor Current Calculation Device
The motor current calculation device 9 is used to calculate a motor current Im passed through the second fan motor 81, and is mounted on a printed board P1 together with a motor-use power supply device 10a for generating a power supply to be supplied to the second fan motor 81 (hereinafter called “motor power supply”) and a drive-use power supply device 10b for generating a power supply to be supplied to the second motor driver 82 (hereinafter called “drive power supply”). The motor-use power supply device 10a and the drive-use power supply device 10b may be a dropper-type power supply, a switching power supply, or of another type. The printed board P1 and the second fan motor device 8 are connected by three harnesses L1, L2, L3 between an interface of the printed board P1 and an interface of the second fan motor device 8. The harnesses L1, L2 are power supply harnesses outputted from the power supply devices 10a, 10b, and the other harness L3 is a GND harness of the second fan motor device 8.
The configuration of the motor current calculation device 9 according to the present embodiment is described below mainly with reference to
(Motor-Use Power Supply Wire)
The motor-use power supply wire 91 is a wire joining the output of the motor-use power supply device 10a and the interface of the printed board P1, and a motor-use power supply outputted by the motor-use power supply device 10a is impressed thereon. The motor power-use supply is impressed on the second fan motor 81 of the second fan motor device 8 via the harness L1. Therefore, the motor current Im passed through the second fan motor 81 flows through the motor-use power supply wire 91.
(Drive-Use Power Supply Wire)
The drive-use power supply wire 92 is a wire joining the output of the drive-use power supply device 10b and the interface of the printed board P1, and a drive-use power supply outputted by the drive-use power supply device 10b is impressed thereon. This drive-use power supply is impressed on the second motor driver 82 of the second fan motor device 8 via the harness L2. Therefore, a drive current Id passed through the second motor driver 82 flows along the drive-use power supply wire 92.
(Current Leveling Unit)
The current leveling unit 93 levels the drive current Id before it passes through the GND wire 94; i.e., the drive current Id flowing on the drive power-use supply wire 92. The current leveling unit 93 is configured from a filter circuit composed of a resistor R1 and a capacitor C1. The resistor R1 is connected in series on the drive-use power supply wire 92, and the capacitor C1 is connected to the drive-use power supply wire 92 in parallel with respect to the resistor R1. More specifically, one end q1 of the capacitor C1 is connected to the drive-use power supply wire 92 on the drive current Id downstream side of the resistor R1, and another end q2 is connected to the GND wire 94.
The resistance of the resistor R1 and the capacitance of the capacitor C1 are herein determined as follows, for example. First, in a drive current Id′ when current leveling unit 93 is not disposed, the drive current Id′ particularly changes, so a frequency f of the portion that should be leveled is measured (
(GND Wire)
The GND wire 94 is a wire joining the GND of the power supply devices 10a, 10b and the interface of the printed board P1, and is connected to the GND of the second fan motor device 8 via the harness L3. Therefore, both the motor current Im passed through the second fan motor 81 and the drive current Id leveled by the current leveling unit 93 and passed through the second motor driver 82 flow through the GND wire 94. For the sake of convenience, the current flowing through the GND wire 94 (i.e., the motor current Im and the leveled drive current Id) will be called a GND current Ig below.
(Current Detecting Unit)
The current detecting unit 95 detects the GND current Ig flowing through the GND wire 94; i.e., the sum of the motor current Im and the leveled drive current Id. The current detecting unit 95 is mainly configured by a shunt resistor Rs, an operational amplifier OP1, or the like. The shunt resistor Rs is connected in series to the GND wire 94. More specifically, the shunt resistor Rs is connected to the GND wire 94 on the GND current Ig downstream side of the other end q2 of the capacitor C1 in the current leveling unit 93. The two input terminals of the operational amplifier OP1 are respectively connected to the two ends of the shunt resistor Rs, and the output terminal is connected to the microcomputer 96. In the operational amplifier OP1 of such description, when the voltage inputted via the input terminals is amplified by a predetermined gain, the amplified voltage is outputted to the microcomputer 96.
(Microcomputer)
The microcomputer 96 comprises CPU, and RAM, ROM or another type of memory. When the microcomputer 96 reads the detection result of the current detecting unit 95, samples this at a predetermined time and A/D converts this. This A/D converted detection result are used to calculation of the motor current Im and determine the drive current Id by the microcomputer 96. The microcomputer 96 functions as a decision unit 96a and a calculation unit 96b in order to perform such actions.
The decision unit 96a determines the detection results of the current detecting unit 95 when the second fan motor 81 is not rotating as the drive current Id. The state in which the second fan motor 81 is not rotating is one in which the second fan motor 81 has not started and rotating speed of the second fan motor 81 is substantially 0 rpm (i.e., a stopped state). Thus, when the second fan motor 81 is stopped, the motor current Im passed through the second fan motor 81 is substantially 0 A, as shown in section A of
It is permissible for the action described above to be performed only when the second fan motor 81 has started. It is also permissible for the action described above to be performed each time the second fan motor 81 stops rotating.
In order for the action described above to be performed, it is first necessary for the decision unit 96a to determine whether or not the second fan motor 81 is in a stopped state. In the present embodiment, an example is given of a case in which the decision unit 96a determines whether or not the second fan motor 81 is in a stopped state based on the detection results of the current detecting unit 95 (i.e., GND current Ig). Specifically, the decision unit 96a determines that the second fan motor 81 has stopped when the value of GND current Ig is close to 0 A and lies within a predetermined range X1, as shown in section A in
Since the motor current Im is passed through the second fan motor 81 on a periodic basis, then the value of the GND current Ig may fall back within the predetermined range X1 even after the decision unit 96a has determined that the second fan motor 81 is rotating (section C in
The calculation unit 96b subtracts the drive current Id determined by the decision unit 96a (i.e., value Y1 in
(1-6) Control Unit
The control unit 11 is a microcomputer comprising CPU, and RAM, ROM, or another type of memory; and a case in which the control unit 11 is provided separately from the microcomputer 96 of the motor current calculation device 9 is used as an example in the present embodiment. The control unit 11 is connected to the four-way switching valve 12, the expansion valve 13, the compressor driver 51, and the first motor driver 71, as shown in
Particularly, the control unit 11 according to the present embodiment is also connected to the second fan motor device 8 and the motor current calculation device 9, and performs a control for these devices. Specifically, the control unit 11 controls the volume of air sent into the room from the second fan 6b by controlling the rotational speed of the second fan motor 81 on the basis of the motor current Im calculated by the motor current calculation device 9. For example, the control unit 11 generates a control signal for turning the switching elements in the second motor driver 82 on and off on the basis of the motor current Im so that the air volume into the room is substantially constant, and the control unit 11 outputs the generated control signal to the second fan motor device 8. A drive voltage based on the control signal from the control unit 11 is thereby outputted to the second fan motor 81 from the second motor driver 82 of the second fan motor device 8, and the second fan motor 81 rotates.
As described above, the control unit 11 uses the motor current Im to control the rotational speed of the second fan motor 81 and control the volume of air sent into the room, whereby it is possible to maintain substantial consistency in the air volume, which is normally susceptible to the length of wire extending into the room from the second blowout opening 25, the air pressure that varies depending on the width of the room interior, and other factors.
(2) Effects
(A)
When the second fan motor 81 is not rotating (i.e., when rotate speed of the second fan motor 81 is 0 rpm), the motor current Im is substantially 0 A; however, the drive current Id flows to the second motor driver 82, and accordingly can be detected. Therefore, in the motor current calculation device 9 according to the present embodiment, the detection results of the current detecting unit 95 when the second fan motor 81 is not rotating are subtracted from the detection results of the current detecting unit 95 when the second fan motor 81 is rotating, and the motor current Im is calculated. The motor current Im can thereby be determined in a simple manner, even when both the motor current Im and the drive current Id flow through the GND wire 94. Moreover, since the detection results of the current detecting unit 95 when the second fan motor 81 is not rotating are used in the calculations, the capacity of the microcomputer 96 functioning as the calculation unit 96b can be reduced.
(B)
The motor current calculation device 9 of the present embodiment further comprises a current leveling unit 93 for leveling the drive current Id before it flows through the GND wire 94. Since the motor current Im and the leveled drive current Id both flow through the GND wire 94, the current detecting unit 95 can thereby detect the sum of the motor current Im and the leveled drive current Id. Consequently, the microcomputer 96 functioning as the calculation unit 96b can determine the motor current Im using stable detection results that include the drive current Id.
(C)
In particular, the current leveling unit 93 in the motor current calculation device 9 can be configured from a so-called filter circuit composed of a resistor R1 and a capacitor Cl. The motor current calculation device 9 is thus capable of leveling the drive current Id using a current leveling unit 93 having a simple configuration.
(D)
When the second fan motor 81 and the second motor driver 82 are built into the second fan motor device 8, it is difficult to separately disposed the the wire on which the motor current Im that has been passed through the second fan motor 81 and the wire on which the drive current Id that has been passed through the second motor driver 82 flow. However, when the motor current calculation device 9 according to the present embodiment is applied in such a case, the detection results outputted by the current detecting unit 95 when the second fan motor 81 is not operating are used in computations as the drive current Id; therefore, the motor current calculation device 9 can calculate the motor current Im with a high degree of accuracy.
(E)
Furthermore, the motor current calculation device 9 can be used for calculating the current of the second fan motor 81 in an air conditioning apparatus 1. Thus, according to the air conditioning apparatus 1 having the motor current calculation device 9, the control unit 11 can perform a control on the basis of an accurate motor current Im calculated by the motor current calculation device 9 so that that, e.g., the volume of air sent into a room remains constant.
(a)
According to the above embodiment, there is described an example of a case in which the air conditioning apparatus 1 is a desiccant-type outdoor air conditioner comprising internal heat exchangers. However, the air conditioning apparatus according to the present invention can also be applied to a desiccant air conditioner in which the heat exchangers are disposed separately from the air conditioning apparatus, or an air conditioner using a system other than a desiccant system.
(b)
According to the above embodiment, there is described a case in which the motor current calculation device 9 comprises a current leveling unit 93 for leveling the drive current Id on the drive-use power supply wire 92. However, even if the drive current Id is not leveled, the motor current calculation device according to the present invention need not include a current leveling unit as long as the motor current Im can be calculated by subtracting the results of the current detecting unit 95 when the second fan motor 81 is not rotating from the results of the current detecting unit 95 when the second fan motor 81 is rotating.
According to the above embodiment, there is described a case in which the current leveling unit 93 is configured from a filter composed of a resistor R1 and a capacitor C1. However, the current leveling unit may be of any configuration as long as the drive current Id can be leveled before flowing through the GND wire 94.
(c)
According to the above embodiment, there is described a case in which the decision unit 96a determines whether or not the second fan motor 81 is in a stopped state, based on the value of the GND current Ig. However, there are no particular limitations as to the method by which the decision unit 96a determines the state of the second fan motor 81. For example, in a case where the second fan motor 81 comprises a position-detecting unit for detecting the position of the rotor relative to the stator, and the second fan motor device 8 is capable of outputting the detection results of the position-detecting unit to the exterior of the second fan motor device 8, then a wire via which the detection results are inputted to the microcomputer 96 may be provided. As a result, the decision unit 96a will be capable of determining whether or not the second fan motor 81 is rotating, based on the detection results of the position-detection unit.
Examples of position-detection units include types in which the position of the rotor is directly detected using a Hall element, a Hall IC, or another magnetic detection sensor; and types in which an induced voltage generated on a drive coil is used to detect the rotor position indirectly.
(d)
According to the above embodiment, there is described a case in which the microcomputers used for the decision unit 96a and the calculation unit 96b of the motor current calculation device 9 are different from the microcomputer constituting the control unit 11. However, the decision unit 96a, the calculation unit 96b, and the control unit 11 may be a single microcomputer. In such instances, a program for setting the drive current, a program for calculating the motor current, and programs for controlling a variety of devices are stored in the memory of the microcomputer. Retrieving and executing any of the memory-resident programs for setting the drive current, for calculating the motor current, or for controlling a variety of devices will enable the microcomputer to function as the decision unit 96a, the calculation unit 96b, or the control unit 11.
(e)
According to the above embodiment, there is described a case in which the second fan motor device 8 includes the second fan motor 81 and the second motor driver 82, and the motor current calculation device 9 detects the motor current Im of the second fan motor 81 in the second fan motor device 8. However, the application of the motor current calculation device according to the present invention is not limited to this example. The motor current calculation device according to the present invention can also be applied to a case in which, for example, the motor and the driver are provided separately, but instead of having a motor current GND wire through which the motor current Im flows and a drive current GND wire through which the drive current Id flows provided separately, the motor current Im and the drive current Id flow through a single GND wire.
(f)
According to the above embodiment, there is described a case in which the motor current calculation device 9 detects a GND current Ig including the motor current Im passed through the second fan motor 81 and calculates the motor current Im from the GND current Ig in order to control the volume of supplying air SA supplied into a room. However, the objective of the current detection performed by the motor current detecting device according to the present invention need not be the second fan motor 81. The motor current calculation device may also be used to detect currents for the first fan motor 7 or the compressor-use motor 5, for example.
The first fan motor 7 maybe included with the first motor driver 71 in a fan motor device, similar to the second fan motor 81.
(g)
According to the above embodiment, a voltage detector 14 may be connected between the output of the motor-use power supply device 10a and the GND, as shown in
(h)
According to the above embodiment, a rotational speed detector 15 for detecting the rotational speed of the second fan motor 81 may also be provided, as shown in
The control unit 11 can thereby calculate the motor torque of the second fan motor 81 using the detected rotational speed of the second fan motor 81 and the calculated motor current Im. Consequently, the control unit 11 can use this motor torque to perform a variety of controls or the like on the second fan motor 81 and other devices included in the air conditioning apparatus 1.
An effect of the motor current calculation device according to the present invention is to make it possible for a motor current to be determined in a simple manner, and a microcomputer functioning as a calculation unit to be reduced in capacity. The device can be used in an air conditioning apparatus.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-298475 | Nov 2007 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2008/070551 | 11/12/2008 | WO | 00 | 5/11/2010 |
