JP2018100792A - Liquid amount detection device and cooling apparatus comprising the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid amount detection device capable of highly accurately measuring a state of liquid stored in a liquid storage container such as refrigerating machine oil of a compressor compressing refrigerant of a cooling apparatus with a simple configuration.SOLUTION: A liquid amount detection device comprises: a compressor being driven by an inverter circuit, compressing refrigerant, and storing refrigerating machine oil therein; a series circuit having a plurality of electrode pairs, being installed with individual one of the plurality of electrode pairs at different positions in a vertical direction in the compressor, having the plurality of electrode pairs connected in series by connecting one electrode of an electrode pair and one electrode of an electrode pair different from the electrode pair by a conductor, and having one end connected to one of power lines of the inverter circuit and the other end connected to a ground potential point; and a detection circuit part detecting a position of an oil level of the refrigerating machine oil by comparing voltages among the electrodes of the individual electrode pairs of the series circuit and detecting differences among the voltages among the electrodes of the individual electrode pairs.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a liquid amount detection device having a plurality of electrode pairs.

  A compressor used for an air conditioner or a refrigerator moves a motor or the like with electric energy and converts the electric energy into heat energy of gas (refrigerant). As a volume compression mechanism for compressing gas, there are a scroll type, a rotary type, and the like, both of which are composed of mechanical parts combined by extremely fine squeezing, and the refrigerant is compressed by moving this. For this reason, oil (refrigerator oil) for lubrication is always required in the gaps between the components of the volume compressor.

  In general, a compressor has a structure in which a volume compression mechanism such as a motor and a scroll is arranged inside a shell casing which is a high-pressure vessel. A predetermined amount of refrigerating machine oil is stored inside the high-pressure vessel, and the mechanical operation of the compressor in which the friction occurs is kept healthy by circulating inside the compressor structure. That is, it is important for maintaining the performance and reliability of the compressor to maintain the state in which the refrigeration oil is normally circulated in the compressor.

  Since the compressor is a device that compresses the refrigerant, the refrigeration oil and the refrigerant inevitably coexist and sometimes mix. The refrigerant passes through the volume compressor and is discharged from the compressor. At that time, a part of the refrigerating machine oil is also discharged.

  As a result, in the refrigerant circuit of the air conditioner, not only the refrigerant but a considerable amount of refrigeration oil circulates. For this reason, in some cases, the amount of refrigeration oil in the compressor may be depleted, causing a problem in the mechanical integrity of the compressor. On the other hand, if the amount of refrigerating machine oil in the compressor becomes too large and the liquid level of the refrigerating machine oil becomes high and interferes with the rotating part of the motor, it becomes a factor of reducing the efficiency of the motor. Therefore, it is desirable that the amount of refrigerating machine oil in the compressor is controlled to an appropriate amount.

  For example, in Patent Document 1, a single capacitance sensor is arranged in a state immersed in a liquid, and the amount of liquid is detected by detecting the capacitance. In Patent Document 2, the first capacitance sensor and the second capacitance sensor are arranged in the liquid reservoir at a position where the influence amount of the metal member is substantially the same, thereby improving the detection accuracy of the liquid amount.

JP-A-2-291484 JP 2014-129802 A

  In liquid quantity detection in such a refrigeration apparatus or compressor, the ratio of noise to the detection signal is large, and accurate measurement is difficult. The present invention has been made to solve the above-described problems, and an object of the present invention is to reduce the influence of noise and enable highly accurate and reliable measurement.

  The liquid amount detection device according to the present invention includes a compressor that is driven by an inverter circuit to compress refrigerant and stores refrigeration oil therein, and has a plurality of electrode pairs, and each of the plurality of electrode pairs is an interior of the compressor. A plurality of electrode pairs are connected in series by connecting one electrode of the electrode pair and one electrode of the electrode pair and one electrode of the other electrode pair by a conductor, and one end of the electrode pair is connected in series. Compare the inter-electrode voltage of each electrode pair of the series circuit with the series circuit connected to one of the power lines of the inverter circuit and the other end connected to the ground potential point, and between the inter-electrode voltage of each electrode pair And a detection circuit unit that detects the position of the oil level of the refrigerating machine oil by detecting the difference.

  According to the liquid amount detection device of the present invention, since the power line of the inverter having a higher voltage than the noise generated in the electrode pair is connected to the electrode pair that is the detection target, the ratio of signal to noise (SN ratio) is reduced. Large measurement can be performed, and a highly accurate and reliable liquid amount can be detected.

It is a figure which shows the installation structure of the liquid quantity detection apparatus and cooling device concerning Embodiment 1 of this invention, (a) is a general view, (b) is a figure which shows a series circuit. 2 shows an example of a voltage waveform and a current waveform of an inverter applied to the liquid amount detection device according to the first exemplary embodiment of the present invention. It is a figure which shows the structural example of the voltage measurement apparatus concerning Embodiment 1 of this invention. It is a figure which shows the structural example of the voltage measurement apparatus concerning Embodiment 1 of this invention. It is a figure which shows the installation structure of the liquid quantity detection apparatus and cooling device concerning Embodiment 2 of this invention, (a) is a general view, (b) is a figure which shows a series circuit. It is a figure which shows the installation structure of the liquid quantity detection apparatus and cooling device concerning Embodiment 3 of this invention, (a) is a general view, (b) is a figure which shows a series circuit. It is a flowchart for the oil level detection of Embodiment 3 of this invention. It is a figure which shows the installation structure of the liquid quantity detection apparatus and cooling device concerning Embodiment 4 of this invention, (a) is a general view, (b) is a figure which shows a series circuit. It is a figure which shows the installation structure of the liquid quantity detection apparatus and cooling device concerning Embodiment 5 of this invention, (a) is a general view, (b) is a figure which shows a series circuit. It is a figure which shows the installation structure of the liquid quantity detection apparatus and cooling device concerning Embodiment 6 of this invention, (a) is a general view, (b) is a figure which shows a series circuit. It is a figure which shows the installation structure of the liquid quantity detection apparatus concerning Embodiment 7 of this invention, (a) is a general view, (b) is a figure which shows a series circuit. It is a figure which shows the installation structure of the liquid quantity detection apparatus concerning Embodiment 9 of this invention, (a) is a general view, (b) is a figure which shows a series circuit.

Embodiment 1 FIG.
FIG. 1A and FIG. 1B are diagrams showing an installation configuration of a liquid amount detection device and a cooling device according to Embodiment 1 of the present invention. FIG. 1A shows a compressor 50, which is an example of a load device, an inverter 36 that drives the compressor 50, and a liquid amount detection device 1, and these constitute a cooling device 500.

  In FIG. 1A, a three-phase AC power supply 31 is connected to a rectifier circuit 33. The rectifier circuit 33, the booster circuit 34, and the smoothing capacitor 35 constitute a converter circuit 32. Both ends of the converter circuit 32 are connected to the N bus LBn and the P bus LBp of the inverter 36, and three-phase power lines LPv, LPu, LPw are connected to the compressor 50 from the inverter circuit. Here, the inverter is also called an inverter circuit.

  The compressor 50 includes a shell casing 51 and a shell inner wall 51 a, and also includes a motor 54 including a stator 57 and a rotor 58. The motor 54 drives a volume compressor 55, and refrigeration oil 56 is used for the compressor. The oil level 59 of the refrigerating machine oil has an appropriate range 200, and the compressor includes a refrigerant suction port 52 and a discharge port 53. A converter circuit, an inverter circuit, a compressor 50, a liquid amount detection device, and the like constitute the cooling device 500.

  1 (a) and 1 (b), the liquid amount detection device 1 has a series circuit 7 having an electrode pair 2b and an electrode pair 2c. The electrode pair 2b and the electrode pair 2c are respectively voltage measuring devices. 15 is connected. The output of the voltage measurement device 15 is connected to the comparison circuit 16, and the comparison circuit 16 and the voltage measurement device 15 constitute a detection circuit unit 6. The electrode pair 2b and the electrode pair 2c are composed of an electrode H and an electrode I, and an electrode J and an electrode K, respectively. The electrode I and the electrode J are connected by a conductor 401. The electrode I constitutes an electrode pair 2b, the electrode J constitutes an electrode pair 2c, and two electrodes constituting different electrode pairs are connected by a connecting line which is a conductor 401.

  Here, the inverter drives the compressor 50 which is a load device, and simultaneously drives the motor 54 which is a load. In the following, a load means a part of a device driven by an inverter, and a load device means the whole device driven by an inverter, but how far is the device and where is a part of the device? May be difficult to judge and shall not be strictly distinguished.

  The operation of the inverter 36 will be described. Power is received from the three-phase AC power source 31, and a DC voltage is generated between LBp and LBn in FIG. 1A by the converter circuit 32 including the rectifier circuit 33, the booster circuit 34, the smoothing capacitor 35, and the like. The positive line of the DC voltage is called a P bus LBp, and the negative line is called an N bus LBn.

  The output line of the inverter, that is, the cable of the input line to the compressor 50 is called a power line. In the first embodiment, the motor 54 has three phases, and there are three power lines LPu, LPv, and LPw. This DC voltage (hereinafter referred to as bus voltage) is converted into alternating current by the inverter 36 and applied to the motor 54 in the compressor 50.

  The operation of the inverter 36 will be described. The inverter 36 is configured such that a switching element such as an IGBT (Insulated Gate Bipolar Transistor) or a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) performs an operation of switching between a connection state and a non-connection state (ON / OFF) with respect to time. The voltage time waveform of each power line is formed from the DC voltage between the P buses.

  FIG. 2 shows an example of an inverter output waveform 301 that is a voltage applied from the inverter 36 to the motor 54 and a current waveform 300 that serves as a command value. The voltage waveform repeats switching at a frequency of several kHz, and the pulse width also changes.

  When this voltage waveform is applied, the current waveform flowing through the motor is a waveform close to a sine wave of 30 Hz to 120 Hz. Such a driving method is called PWM (Pulse Width Modulation) control. The voltage switching frequency is higher than the current frequency at which the motor is driven. The inverter 36 is controlled by an inverter control unit (not shown).

  At this time, a current having a waveform close to a sine wave flows through the motor, but the voltage applied from the inverter to the motor is a continuous high-frequency pulse. Therefore, an alternating current with the PWM frequency is output to the power line of the inverter. At the same time, there is a frequency component of the motor rotation.

  When the potential difference between the ground potential point and the power line is applied to the detection target to the electrode as shown in FIG. 1A, voltage fluctuation of the frequency component due to the received AC voltage exists in addition to the PWM frequency. . Among these frequency components, the PWM switching frequency is the highest.

  The compressor 50 is mainly composed of a motor 54 and a volume compressor 55 driven to rotate by the motor 54. In FIG. 1A, a scroll type compressor is shown as the volume compressor 55, but other types of volume compressors such as a rotary type or a reciprocating type may be used. The compressor 50 sucks the refrigerant from the suction port 52, compresses it with the compressor 50, and discharges it from the discharge port 53.

  The motor includes a stator 57 fixed to the shell casing 51 of the compressor 50 and a rotor 58 at the center so as to be surrounded by the stator. The cooling device 500 includes a refrigerant circuit (not shown), a heat exchanger (not shown), and the like depending on the application.

  In order to facilitate understanding of the structure, the stator 57 is shown by a cut surface including a plane including the rotation axis of the rotor 58. Below the rotor 58, there is an oil suction port for sucking the refrigeration oil 56 and circulating it to each part of the compressor 50 such as a positive displacement compressor (not shown because it is below the oil level 59).

  As shown in FIG. 1A, the shell housing 51 of the compressor 50 has a shape that is longer in the vertical direction as the rotation axis of the motor than in the horizontal direction as the rotation surface of the motor 54. 56 are stored. In the first embodiment, the compressor has a vertically long structure, the motor rotating shaft is vertically long, and the rotating surface is horizontally horizontal. However, the present invention is not limited to this shape. The present invention can be applied to a horizontally long compressor, a rotating surface having a vertical structure, and a rotating shaft having a horizontal structure.

  In the first embodiment, the shell casing 51 corresponds to a liquid storage container. The refrigerating machine oil 56 is sucked from an oil suction port provided at the lower part of the rotor 58 and circulates inside the compressor 50. The oil level 59 of the refrigerating machine oil 56 rises and falls according to the consumption of refrigerating machine oil by the compressor and the recovery operation for recovering the amount of refrigerating machine oil.

  In the first embodiment, as will be described below, an upper limit and a lower limit of the position of the oil level 59 are provided, and an appropriate range 200 is provided between the upper limit and the lower limit so that the oil level 59 is maintained within the appropriate range. To manage.

  The upper and lower limits of the refrigerating machine oil are indicated by broken lines in the figure. The lower limit of the oil level position was the oil suction port (inside the refrigerator oil 56). If the amount of refrigeration oil decreases until the oil level 59 is below the oil suction port, the refrigeration oil cannot be drawn and circulated in the compressor.

  In addition, the upper limit of the oil level position was set to a position below the protruding portion, which is a portion where the upper diameter of the rotor 58 of the motor is large. If the oil level exceeds the upper limit and the protrusion at the top of the rotor of the motor is immersed in the refrigeration oil, the resistance of the refrigeration oil can affect the motor torque and reduce the compressor efficiency. It is because there is sex.

  As described above, the proper range of the amount of the refrigerating machine oil in the first embodiment, that is, the proper range of the position of the oil surface 59 is above the oil suction port and below the protruding portion of the upper part of the rotor 58 of the motor. Electrode pairs are arranged near the upper and lower limit positions, respectively. The two electrode pairs are arranged at different positions in the vertical direction.

  More specifically, as an example of the installation position, it is preferable to arrange the first electrode pair 2b composed of the electrode H and the electrode I at a position slightly below the upper limit value, that is, the lower end of the rotor of the motor. . In order to clarify the reference numerals, the series circuit 7 is shown in FIG. The second electrode pair 2c composed of the electrode J and the electrode K is preferably disposed at the lower limit, that is, a position slightly above the oil suction port. In this case, the electrode pair 2b and the electrode pair 2c are respectively arranged at different positions in the vertical direction inside the compressor or inside the housing shell.

  In the first embodiment, the electrode pair 2b and the electrode pair 2c are shown in which two metal plates are spaced apart and arranged in parallel up and down. As the electrical property of the capacitor, the shorter the distance between the electrodes, the larger the capacitance, and the SN ratio (signal to noise ratio) of the detector can be increased. Therefore, the shorter the distance between the electrodes, the better. However, if the distance is too short, it becomes difficult for oil to enter between the electrodes or the oil between the electrodes becomes difficult to be discharged.

  In the first embodiment, the separated metal plates are arranged. However, oil may flow in and out through a part between the electrodes with an insulator interposed therebetween. For example, by sandwiching a member whose both surfaces are parallel to each other, the sandwiched one serves as a positioning reference. Therefore, there is an effect that the arrangement accuracy such as the distance between the electrodes and the parallelism can be improved. A member provided with a hollow part and having only an end part is suitable for detecting a difference in capacitance because a sufficient amount of oil can flow into the inside.

  In addition, it is preferable that the electrode area is large because the capacitance becomes high and a detection signal with a high S / N ratio can be obtained. However, there is a restriction that the electrode area is arranged inside the shell casing 51 of the compressor. Therefore, it may be arranged inside the shell housing 51 so as not to hinder the operation or arrangement of other components, such as making the electrode shape elongated or making the electrode a curved surface along the shape of the shell inner wall 51a.

  Connection lines from the electrode H, the electrode I, the electrode J, and the electrode K are drawn out from the inside of the shell casing 51 through the glass terminal T2. In Embodiment 1, since the electrode H, the electrode I, the electrode J, and the electrode K are drawn out separately, a total of four connection lines are drawn out. A wiring may be provided inside, two electrode pairs may be connected in series inside the compressor, and three connection wires may be drawn through the glass terminals. Electrode I and electrode J are connected by conductor 401. In this case, connection lines are drawn out from the three locations of the electrode H, the electrode I and the electrode J connected by the conductor 401, and the electrode K.

  In the first embodiment, a portion constituted by the electrode pair 2b, the electrode pair 2c, and a connection line connecting them is the series circuit 7. The liquid amount detection device 1 includes a series circuit 7 including an electrode pair and a connection line, a detection circuit unit 6 that detects a voltage of the electrode pair or a voltage difference, and a connection line to the housing. The detection circuit unit 6 includes a voltage measurement device 15 and a comparison circuit 16.

  The electrode H that is one end of the electrode pair 2b and the electrode pair 2c connected in series is connected to the U phase of the three-phase power lines connecting the inverter 36 and the compressor. In the case of a three-phase motor, there are three power lines, a U phase, a V phase, and a W phase, which may be connected to any of them. On the other hand, the electrode K which is the other end of the pair of electrodes connected in series is connected to the ground potential point.

  When the shell casing 51 of the compressor 50 is grounded, the electrode K and the shell casing 51 may be connected. In FIG. 1 (a) and FIG. 1 (b), the electrode H and the power line are connected outside the compressor. However, if the power line and the electrode H are connected, they can be connected inside the compressor. Good. If connected in this way, there is an effect of reducing the number of connection lines drawn from the inside of the compressor.

  In FIGS. 1A and 1B, the connection line from the electrode K is connected to the ground potential point outside the shell casing 51, but the shell casing of the compressor 50 is grounded. Can also be connected to the shell housing 51 from the electrode K inside the compressor. In such a configuration, there is an effect that the number of wirings drawn through the glass terminals can be further reduced.

  The above is the configuration of the first embodiment. In order to reduce the influence of noise, a twisted pair cable or a coaxial cable may be used for the connection between the voltage detection measuring device and the electrode pair, and also the connection between the circuits.

  A voltage that is switched at the switching frequency of the PWM control shown in FIG. 2 is applied to the power line of the inverter 36, and a current that vibrates at the driving frequency of the motor flows. Furthermore, the three-phase AC power supply 31 that the inverter is receiving vibrates at the frequency of the AC power supply.

  Therefore, the voltage between the U phase and the ground potential applied to both ends of the electrode pair 2b and the electrode pair 2c connected in series includes the AC frequency of the motor 54, the frequency of the three-phase AC power supply 31, the PWM control of the inverter. There may be a plurality of frequency components such as Of these, the PWM control switching frequency is the highest.

  For accurate measurement, it is necessary to avoid changes in measurement results due to the effect of connecting the measurement system. For this reason, it is necessary to increase the impedance of the measurement system with respect to the impedance to be measured. In the first embodiment, the measurement system is the detection circuit unit 6, and the measurement target is the series circuit 7.

  The electrode pair of the series circuit 7 has a property that the impedance becomes low at a high frequency. In the first embodiment, only one phase of the inverter power lines is connected to the series circuit 7, and the interelectrode voltage is detected by the detection circuit unit 6. Therefore, the impedance of the detection circuit unit 6 can be further reduced by applying a voltage waveform that is switched at high speed.

A measurement method for detecting the capacitance value of the electrode pair and detecting the position of the oil surface 59 of the refrigerating machine oil 56 according to the configuration of the first embodiment will be described below.
The two electrode pairs 2b and 2c each form a capacitor. When an AC voltage is applied to two capacitors connected in series, the voltage is divided in proportion to the inverse of the capacitance of the capacitor.

The capacitance of the electrode pair 2b and the electrode pair 2c is C _2b and the voltage between the C _2c electrodes is V _2b and V _2c , respectively, and V ₀ is at both ends of the electrode pair 2b and the electrode pair 2c connected in series. When the voltage is applied, the relationship is as shown in (1) and (2), and V _2b and V _2c are as shown in (3) and (4).

If the values of the interelectrode voltage V _2b and the interelectrode voltage V _2c (AC amplitude) are measured, the values of C _2b and C _2c can be known. Actually, the capacitance measurement values of the electrode pair 2b and the electrode pair 2c include the stray capacitance Cs. However, since the stray capacitance Cs is caused by the structure of the device, before the capacitance is detected. The values of C _2b and C _2c can be obtained by evaluating and converting the values.

In the liquid amount detection device 1 according to the first embodiment, the interelectrode voltage V _2b and the interelectrode voltage V _2c are measured by the voltage measuring device 15 and compared by the comparison circuit 16. The comparison circuit 16 outputs the comparison result. Specifically, the difference between the interelectrode voltage _V2b and the interelectrode voltage _V2c or the ratio between the two is output. The structure of the voltage measuring device 15 will be described in more detail. 3 and 4 show two examples of the configuration of the voltage measuring device 15 according to the first embodiment.

  The voltage measuring device shown in FIG. 3 includes a detection-side rectifier circuit 23 to which a signal is input, a voltage dividing circuit 22, a filter capacitor 28, an insulation amplifier 24, an amplifier 25, a low-frequency filter 21a, and a voltage detection circuit 20. . The low frequency filter 21 a and the voltage detection circuit 20 constitute a voltage detection unit 21.

The voltage measuring device shown in FIG. 4 includes a voltage dividing circuit 22, a detection side rectifier circuit 23, a filter capacitor 28, an insulation amplifier 24, an amplifier 25, a low frequency filter 21a, and a voltage detection circuit 20. The low frequency filter 21 a and the voltage detection circuit 20 constitute a voltage detection unit 21.
1A and 1B, one voltage measuring device 15 is provided for each electrode pair.

First, the configuration of the voltage measuring device 15 according to the first embodiment shown in FIG. 3 will be described. The interelectrode voltage _V2b and the interelectrode voltage _V2c are input to the detection-side rectifier circuit 23 in FIG. The interelectrode voltage V _2b and the interelectrode voltage V _2c are alternating voltages. The AC signal passes through the detection-side rectifier circuit 23, and the bipolar signal is converted into a unipolar signal, that is, a signal having only a positive polarity or a negative polarity.

  Next, the voltage drops through the voltage dividing circuit 22. Thereafter, it passes through the filter capacitor 28 and the insulation amplifier 24 further. If the reference potential of the electrode pair is equal to the reference potential of the control system, the insulation amplifier 24 can be omitted.

  The signal that has passed through the insulation amplifier 24 is amplified by the amplifier 25 and input to the voltage detection unit 21. The voltage detection unit 21 includes a voltage detection circuit 20 and a low frequency filter 21a for removing high frequency components. The low frequency filter 21a averages fine vibrations of the signal.

  Here, when the detection target is an oil level position and the time constant of the change is sufficiently long with respect to the current and voltage frequencies, the cutoff frequency of the low frequency filter 21a is set to be as low as several Hz. Is preferred. With this setting, the detection accuracy can be improved by increasing the detection time to about 1 second and performing the averaging process.

  The voltage measuring device shown in FIG. 4 has the order of the detection-side rectifier circuit 23 and the voltage dividing circuit 22 reversed with respect to FIG. Therefore, there is an advantage that the high voltage applied directly to the power line of the inverter is not applied to the rectifier circuit.

  As an example of specific numerical values, when a voltage of 100 V is applied to both ends of the detection-side rectifier circuit 23 in FIGS. 3 and 4, the withstand voltage of at least 100 V or more is applied to the detection-side rectifier circuit 23 in the configuration of FIG. is necessary. When analog signal processing such as an operational amplifier is used for the detection-side rectifier circuit 23 or digital signal processing is used, it is preferable to provide the detection-side rectifier circuit 23 after the voltage dividing circuit 22 as shown in FIG.

  The signal flow of the circuit shown in FIG. 4 will be briefly described. The interelectrode voltage input to both ends of the voltage dividing circuit 22 is divided by the voltage dividing circuit 22, and then passes through the detection side rectifier circuit 23 to be rectified. After that, after having passed through the filter capacitor 28 and the insulation amplifier 24 with the same structure as in FIG. 3, the signal passes through the amplifier 25 and is input to the voltage detection unit 21. The voltage detection unit 21 includes a voltage detection circuit 20 and a low frequency filter 21a.

  Since the voltage measuring apparatus of FIGS. 3 and 4 includes the detection-side rectifier circuit 23, the interelectrode voltage is output to the comparison circuit 16 as a DC value. Therefore, it is possible to compare the measured interelectrode voltage. In the first embodiment, the comparison circuit 16 is used to detect the difference between the electrode voltages of the electrode pair 2b and the electrode pair 2c. However, the subtractor circuit subtracts the other electrode voltage from the one electrode voltage. Also good. Further, an adder circuit may be used by using a circuit in which the sign of one signal is reversed.

  In the first embodiment, the absolute values of the voltage between the electrodes 2b and 2c are measured, and the voltage values are compared at the subsequent stage. According to the method described below, the absolute value of the voltage is Without measuring, it is possible to detect the difference between the two and detect the position of the oil level.

  In the first embodiment, the proper range is when the oil level 59 is at a position between the electrode pair 2b and the electrode pair 2c in the vertical direction, and is not the proper range otherwise. That is, when the oil level 59 is below the electrode pair 2c in the vertical direction and when it is above the electrode pair 2b in the vertical direction, it is out of the proper range. In practice, it is at least necessary to detect whether the oil level is in the proper range or not.

  When the oil level 59 is below the electrode pair 2c in the vertical direction, the gap between the two electrode pairs is filled with gas. Further, when the oil level 59 is above the electrode pair 2b in the vertical direction, the gap between the two pairs of electrodes is filled with refrigerating machine oil. In these two cases, the capacitances of the electrode pair 2b and the electrode pair 2c do not change, and when the inter-electrode voltage of the electrode pair 2b and the inter-electrode voltage of the electrode pair 2c are measured, substantially equal values are detected.

  On the other hand, when the oil level is at a position between the electrode pair 2b and the electrode pair 2c in the vertical direction, which is a position within the appropriate range, the gap between the electrodes of the electrode pair 2c is filled with refrigerating machine oil, and the gap between the electrodes of the electrode pair 2b is Filled with gas. In this case, the capacitances of the electrode pair 2b and the electrode pair 2c are different, and a significant difference is detected when the voltage between the electrodes of the electrode pair 2b and the electrode pair 2c is compared.

  Whether or not a significant difference has been detected can be determined, for example, by setting a threshold value in advance and determining whether or not the magnitude of the detected difference exceeds the threshold value. Further, it is preferable to output the determination result.

From the above, the inter-electrode voltage V _2b and the inter-electrode voltage V _2c of the electrode pair 2b and the electrode pair 2c are compared. can do. In this way, whether or not the oil level 59, that is, the amount of the refrigerating machine oil 56 is within an appropriate range, without having to know the absolute value of the voltage between the electrodes only by comparing the voltage between the electrodes 2b and 2c. Can be judged.

  The method for detecting the voltage value difference between the electrodes without measuring the voltage value between the electrodes described in the first embodiment has an effect of reducing the number of voltage measuring devices 15. Further, there is an effect that a device for switching the electrode pair to be measured by the relay switch can be omitted. Here, the relay switch means a switch having a function of switching between connection and non-connection between the contacts by an external signal, command, input or the like. The relay switch is sometimes called a relay, a relay switch, a relay, or the like, but in the following, a relay switch is used.

  An example of a method for managing refrigerating machine oil in the operation of a refrigerator including a compressor, a cooling device, and a cooling device will be described. Whether the amount of refrigerating machine oil is within an appropriate range is monitored for a certain time, preferably at intervals of several seconds to several minutes, and when it is detected that the amount of refrigerating machine oil is outside the proper range, the device Stop driving.

  Alternatively, in addition to stopping the operation, the cooling device is controlled so that the oil level rises slightly below the position of the electrode pair 2c from the position of the electrode pair 2b, so that the oil level position of the refrigerating machine oil is within an appropriate range. An operation such as performing an oil recovery operation may be performed.

  According to the liquid amount detection device of the present invention, since the inverter power line is connected to the electrode pair, the voltage of the inverter power line that generates a signal is higher than the noise caused by the compressor driving power generated around, Accurate oil level detection with a high SN ratio can be performed. Therefore, it can be known without a large time delay that the amount of the refrigerating machine oil has fallen below the appropriate range, and the compressor can be stopped without delay to maintain the apparatus. In addition, there is an effect that the recovery operation time of the refrigeration oil can be adjusted and the oil level can be maintained in an appropriate range.

  Further, if the detection device of the present invention is used during the recovery operation of the refrigeration oil or immediately after the recovery operation, the oil level 59 is outside the proper range before the recovery operation of the refrigeration oil, and within the proper range after the recovery operation. It can be confirmed with high reliability.

  As a result, it is possible to prevent situations such as operating the compressor in a state where the recovery operation of the refrigerating machine oil for the required time has not been performed, or the refrigerating machine oil has been recovered for a longer time than necessary. There is an effect that the compressor can be operated more reliably.

  As described above, according to the configuration described above, the power line of the high-voltage inverter is connected to the electrode pair, and the potential difference between the electrodes at both ends of the electrode pair is measured, so that a signal larger than noise can be detected. . Therefore, it is possible to detect a signal with a high S / N ratio with respect to a noise source such as a compressor driving current, and to obtain an effect that measurement with higher accuracy is possible.

  Further, as shown in the present embodiment, an inverter that drives a load device is used as a power source for generating a signal. Therefore, it is possible to construct a liquid amount detection device that is simple and low-cost, highly accurate and highly reliable by wiring from an inverter that drives the device without separately preparing a power source for generating a signal. There is.

Embodiment 2. FIG.
FIG. 5A and FIG. 5B are configuration diagrams of Embodiment 2 of the present invention. Since the configurations and operations of the compressor 50 and the inverter 36 are the same as those in the first embodiment, detailed description thereof will be omitted. Also in the second embodiment, the converter circuit, the inverter circuit, the compressor, the liquid amount detection device, and the like constitute the cooling device 500. The cooling device 500 includes a refrigerant circuit (not shown), a heat exchanger (not shown), and the like depending on the application.

  5 (a) and 5 (b), the inverter 36 and the compressor 50 are connected by three-phase power lines LPv, LPu, LPw, and the compressor 50 includes a shell casing 51 and a shell inner wall 51a. Yes. Further, a motor 54 composed of a stator 57 and a rotor 58 and a volume compressor 55 driven by the motor 54 are provided. Here, the inverter is also called an inverter circuit.

  Further, it has a refrigerant inlet 52 and a refrigerant outlet 53. Refrigerating machine oil 56 is stored below the oil level 59 inside the compressor. In the second embodiment, the shell casing 51 corresponds to a liquid storage container.

  The inverter 36 is supplied with electric power from a three-phase AC power supply (not shown) as in the first embodiment, drives the motor 54 inside the compressor 50, and the volume compressor 55 is operated by driving the motor 54. Yes. The liquid amount detection device 1 includes a voltage dividing circuit 22a, an insulation amplifier 24a, an addition circuit 29, a detection-side rectifier circuit 23a, a low frequency filter 21a, an insulation amplifier 24b, and a control circuit 61.

  The voltage dividing circuit 22a, the insulation amplifier 24a, the addition circuit 29, the detection side rectifier circuit 23a, the low frequency filter 21a, the insulation amplifier 24b, and the control circuit 61 constitute a detection circuit unit 6a. The series circuit 7 includes an electrode pair 2b and an electrode pair 2c. The electrode pair 2b includes an electrode H and an electrode I. The electrode pair 2 c includes an electrode J and an electrode K.

  For easy understanding of the reference numerals, the series circuit 7 is shown in FIG. The electrode pair 2b disposed inside the compressor is composed of an electrode H and an electrode I, and the electrode pair 2c is composed of an electrode J and an electrode K.

  The electrode pair 2b and the electrode pair 2c are connected in series by connecting the electrode I and the electrode J with a conductor 401a, and two electrode pairs connected in series constitute a series circuit. Both ends of the series circuit are an electrode H and an electrode K. In this case, the electrode pair 2b and the electrode pair 2c are arranged at different positions in the vertical direction inside the compressor or the shell casing.

  The W phase which is one phase of the power lines of the inverter 36 is connected to the electrode H which is one end of the series circuit 7 which is a plurality of electrode pairs connected in series, and the electrode K which is the other end of the series circuit 7 is grounded. Connected to potential point. The U phase and the V phase may be connected to the electrode H. A signal line is drawn out from the shell housing 51 of the compressor from the connection between the electrode I and the electrode J, and serves as a reference potential for the measurement system.

  In other words, the potential of the connection line between the electrode pair 2b and the electrode pair 2c is the reference potential of the detection circuit unit. In this case, the electrode I and the electrode J are connected by the conductor 401a. The potential of the conductor 401a connecting the electrode I and the electrode J is the reference potential of the measurement system.

  The electrode I constitutes an electrode pair 2b. The electrode J constitutes an electrode pair 2c. That is, the electrode I and the electrode J constitute different electrode pairs. The electrode pair 2b and the electrode pair 2c are connected in series by connecting between two electrodes constituting different electrode pairs by a conductor 401a.

  The reference potential of this measurement system does not necessarily coincide with the ground potential point to which the shell housing 51 of the compressor 50 is connected. Even when three or more electrode pairs are included, the same effect can be obtained if the potential of any one of the two electrodes constituting the different electrode pairs and the conductor connecting the electrodes is set as the reference potential of the detection circuit unit.

  In the second embodiment, the potential of the conductor 401a which is a connection line connecting between the electrode pair 2b and the electrode pair 2c is used as the reference potential of the measurement system. An example of the case where the electrode and the electrode are not connected by the connection line will be given.

  For example, when a shell casing made of a conductor is used as an electrode, a first electrode facing a part of the shell casing is provided as a first electrode pair and facing another part of the shell casing. A second electrode can be provided to form a second electrode pair.

  In this case, the portion facing the first electrode is a portion of the first electrode pair in the shell housing, and the portion facing the second electrode pair is the second electrode in the shell housing. This is a portion of the electrode pair. Therefore, the shell casing connects the first electrode pair and the second electrode pair by the shell casing itself.

  In this case, a portion connecting the portion of the first electrode pair of the shell casing and the portion of the second electrode pair of the shell casing is a conductor connecting the electrode pair and the electrode pair. The two electrode pairs may not be separated in the vertical direction, but are installed at different positions in the vertical direction.

  In the second embodiment, the electrode pair 2b, the electrode pair 2c, and the conductor 401a therebetween constitute the series circuit 7, and the portion connected to the subsequent stage is the detection circuit unit 6a. Specifically, the detection circuit unit 6a is configured by the voltage dividing circuit 22a, the insulation amplifier 24a, the addition circuit 29, the detection-side rectification circuit 23a, the low-frequency filter 21a, the insulation amplifier 24b, and the control circuit 61.

  In the second embodiment, the detection circuit unit detects a difference in voltage between the electrodes 2b and 2c included in the series circuit 7. Moreover, the voltage between electrodes is compared. The connection portions of the electrodes H and K, and the electrodes I and J are connected to the voltage dividing circuit 22a. The voltage dividing circuit 22a divides the voltage across the electrode pair 2b and the electrode pair 2c by four resistors R4 and R3, and R2 and R1, respectively. The values of Expression (5) and Expression (6) are output from the voltage dividing circuit.

The two signals after the voltage division are amplified by the two isolation amplifiers 24a. By the circuit configuration of that after the addition circuit 29, the voltage value of the inter-electrode voltage V _2b divided voltage value and the inter-electrode voltage V _2c was the sign of the divided negation is added. Further, after passing through the detection-side rectifier circuit 23a and the low-frequency filter 21a, it passes through the insulation amplifier 24b and is input to the control circuit 61. The output of the adder circuit is

となる。

It becomes.

  If the electrode pairs are configured in exactly the same way and the capacitances of the electrode pair 2b and the electrode pair 2c are the same, the voltage waveforms input to the two amplifiers will be alternating waveforms of the same amplitude with the positive and negative reversed. Therefore, when the voltage waveforms are added, if the capacitances of the electrode pair 2b and the electrode pair 2c are the same, it becomes zero, and if they are different, a significant value other than zero is output. In this way, the voltage between the electrodes is compared. Alternatively, a difference in voltage between electrodes can be detected.

As a specific implementation method, for example, a threshold value is set in advance, and it can be determined whether or not the detected value is a significant value depending on whether or not the threshold value is exceeded.
The voltage dividing circuit has an effect of protecting a device having a low withstand voltage by dropping a voltage applied to the device.

  In the control circuit 61, when a significant value is detected, there is a difference in capacitance between the electrode pair 2b and the electrode pair 2c, that is, the oil level is vertical between the electrode pair 2b and the electrode pair 2c. Judgment that it is in the position and within the appropriate range. If there is no significant difference, the control circuit determines that the oil level is not in the position between the electrode pair 2b and the electrode pair 2c in the vertical direction.

  That is, it is determined that the oil level is outside the proper range, and the compressor is stopped to protect the device. Alternatively, control such as performing an oil level recovery operation for recovering the amount of the refrigerating machine oil 56 is performed.

  The effect of the configuration of the second embodiment will be described in more detail. In the embodiment shown in FIGS. 5A and 5B, the control circuit 61 receives a signal after passing through the detection-side rectifier circuit 23a (half-wave rectifier) and the low-frequency filter 21a. The control circuit 61 can receive a signal close to direct current, so that judgment and signal exchange are easy.

  If the voltage detection circuit is configured as in the second embodiment, it is possible to detect whether or not there is a difference between the capacitances of the two electrode pairs without measuring the absolute value of the voltage, that is, the capacitance value. can do. In addition, since almost the same voltage with positive and negative reversed is detected, it is possible to detect the oil level with a high S / N ratio without using the detection side rectifier circuit 23a.

  Next, in the configuration of the second embodiment, a method for reducing the influence of the installation error and the shape error between the electrode pair 2b and the electrode pair 2c on the measurement will be described. It is desirable that the two electrode pairs 2b and 2c have the same shape, specifically the electrode area and the electrode pair gap length. This is for determining the position of the oil level depending on whether the capacitance value between the electrodes is the same or different.

  Actually, there is a possibility that the capacitance values of the two electrode pairs are slightly different from each other due to an installation error, a shape error, or a variation in manufacturing. Specifically, when the opposing electrodes are arranged so as to be shifted from each other, the distance between the electrodes or the area of the electrodes is different between the electrode pair 2b and the electrode pair 2c.

  In addition, when more accurate detection is required, the required tolerance of grounding error or shape error is narrowed, and the tolerance is reduced, for example, the tolerance is reduced. Cause an increase in manufacturing time and a decrease in yield.

  In the configuration of the second embodiment, it is possible to reduce or alleviate the influence of installation error or shape error by calibrating the detector. For example, in the case of FIG. 5A and FIG. 5B, a means for adjusting R5 and R6 is provided such that the values of R5 and R6 of the adder circuit 29 are variable resistors. Can be achieved. The same effect can be obtained by adjusting the ratio of R2 to R1 and the ratio of R3 to R4. In this case, R5 and R6, which are variable resistors, are calibration units. Alternatively, R1, R2, R3, R4, means for adjusting the ratio of R1 and R2, and means for adjusting the ratio of R3 and R4 are calibration units.

  A specific example is given. For example, it is assumed that the electrode pair 2b and the electrode pair 2c have the same shape and material, and both are filled with gas and have the same capacitance. In this case, for example, R2 / (R1 + R2) = R3 / (R3 + R4) and R7 / R5 = R7 / R6 are set so that the expression (7) does not become a significant value, or a significant difference is detected in the interelectrode voltage. Set not to be done.

  In actual operation, before the electrode pair is installed in the apparatus, the two electrode pairs are both filled with gas, or the two electrode pairs are both filled with liquid. Compare the interelectrode voltage of two electrode pairs. R2 / (R1 + R2) and R3 / (R3 + R4) or R7 / R5, R7 / R6 are adjusted so that the expression (7) does not become a significant value while observing the comparison result. Thereafter, the operation of the apparatus is preferably started.

  In general, in order to avoid a change in detection result due to the connection of a detection circuit, it is necessary to make the input impedance of the detection circuit sufficiently higher than the impedance to be detected. In the conventional liquid amount detection device, there is a problem that the impedance of the circuit portion connected to the electrode pair must be higher than the capacitance of the electrode pair.

  A typical numerical value is given as an example of the capacitance of the electrode pair. When the electrode pair is configured in the compressor, a capacitor in which the area of the two flat electrodes is 10 cm 2 is formed by providing a gap (for example, 1 mm) that allows oil to flow in and out without stagnation. The capacitance is between 8 pF and 9 pF. The capacitance is set to a value from 10 pF to several tens of pF. The PWM frequency of the inverter is often set to several kHz.

  Since the impedance of the electrode pair is inversely proportional to the frequency, it becomes 10 MΩ to several tens of MΩ. Therefore, in the conventional liquid amount detection device, the impedance of the voltage dividing circuit needs to be at least this value and at least 100 MΩ or more.

  Further, by adjusting the resistance provided in the voltage dividing circuit or the adding circuit, that is, by providing a calibration unit, it is possible to increase the tolerance of the size of the electrodes and the tolerance of the arrangement accuracy of the electrodes at the time of manufacture.

  From the above, in the liquid amount detection device for detecting the difference in the interelectrode voltage of the plurality of electrode pairs, the shape and size of the electrode can be obtained by providing the calibration means between the two interelectrode voltages in the liquid amount detection device. The required accuracy can be relaxed with respect to the specifications and the accuracy of the arrangement. Or, there is less demand for arrangement, shape, and size. There is an effect.

  Furthermore, since the inverter power line is connected to one end of the series circuit, the output of the signal can be made larger than the noise generated by the compressor, such as a compressor drive power supply, and measurement with a high S / N ratio can be achieved. It can be carried out. Thereby, it is possible to compare the capacitance with high accuracy and high reliability and detect the difference, and to detect the oil level with high accuracy and high reliability.

Embodiment 3 FIG.
In the third embodiment, the series circuit 7 includes three electrode pairs. FIGS. 6A and 6B show a configuration according to the third embodiment. Since operations of the inverter 36 and the motor 54 driven by the inverter 36 and the compressor 50 are the same as those in the first embodiment, the description thereof is omitted. In the third embodiment, the shell casing 51 corresponds to a liquid storage container.

Here, the inverter is also called an inverter circuit. Also in the third embodiment, the converter circuit, the inverter circuit, the compressor, the liquid amount detection device, and the like constitute the cooling device 500. The cooling device 500 includes a refrigerant circuit (not shown), a heat exchanger (not shown), and the like depending on the application.

  In FIG. 6A and FIG. 6B, the three-phase AC power supply 31 is connected to the rectifier circuit 33. The rectifier circuit 33, the booster circuit 34, and the smoothing capacitor 35 constitute a converter circuit 32. Both ends of the converter circuit 32 are connected to the N bus LBn and the P bus LBp of the inverter 36, and three-phase power lines LPv, LPu, LPw are connected to the compressor 50 from the inverter circuit.

  The compressor 50 includes a shell casing 51 and a shell inner wall 51 a, and also includes a motor 54 including a stator 57 and a rotor 58. The motor 54 drives a volume compressor 55, and refrigeration oil 56 is used for the compressor. The refrigerating machine oil is stored in the compressor below the oil level 59. The compressor includes a refrigerant suction port 52 and a discharge port 53.

  The liquid amount detection device 1b includes a series circuit 7 and a detection circuit unit 6b. As shown in FIG. 6B, the series circuit 7 includes an electrode pair 2b composed of an electrode H and an electrode I, an electrode pair 2c composed of an electrode J and an electrode K, and an electrode pair 2d composed of an electrode L and an electrode M. . The detection circuit unit 6b includes a relay switch 4a, a voltage measurement device 15, a relay switch control unit 63, a determination unit 64, and a storage unit 65.

  In order to clarify the reference numerals, a series circuit is separately illustrated in FIG. In the third embodiment, the electrode pair 2b, the electrode pair 2c, and the electrode pair 2d, and the conductor 401b and the conductor 401c that connect between them constitute the series circuit 7. The electrode I constituting the electrode pair 2b and the electrode J constituting the electrode pair 2c are connected by a connection line serving as the conductor 401b. The electrode K that constitutes the electrode pair 2c and the electrode L that constitutes the electrode pair 2d are connected by a connection line serving as a conductor 401c.

  That is, two electrodes constituting different electrode pairs are connected to each other by a conductor. With this connection, the electrode pair 2b, the electrode pair 2c, and the electrode pair 2d are connected in series.

  The latter part connected to the series circuit 7 is a detection circuit part. Specifically, the relay switch 4a, the relay switch control unit 63, the voltage measurement device 15, the determination unit 64, and the storage unit 65 constitute the detection circuit unit 6b. The liquid amount detection device includes a series circuit 7, a detection circuit unit 6b, a connection line to the ground potential point, and the like.

  The electrode pair 2b, the electrode pair 2c, and the electrode pair 2d have a parallel plate shape so that the surface of the electrode is parallel to the liquid surface and at different positions in the vertical direction inside the compressor. Has been placed. The electrode pair 2 b is disposed at the upper limit of the appropriate range of the refrigerating machine oil 56. The electrode pair 2c is disposed slightly above the lower limit of the appropriate range of the oil level 59.

  The electrode pair 2d is disposed at the lower limit of the appropriate range of the oil level 59 of the refrigerator oil 56. In this case, the electrode pair 2b, the electrode pair 2c, and the electrode pair 2d are arranged at different positions in the vertical direction inside the compressor or inside the shell casing. Here, the electrode pairs do not necessarily have to be arranged in the order of electrical connection in the vertical direction. For example, even if the electrode pair 2b, the electrode pair 2d, and the electrode pair 2c are arranged in the vertical direction from the upper side to the lower side, the effect of the present invention can be obtained by comparing the voltage between the electrodes by changing the order.

  The wiring drawn from each electrode pair is connected in series in the order of electrode pair 2b, electrode pair 2c, and electrode pair 2d. Electrode I and electrode J, and electrode K and electrode L are connected outside shell housing 51. A V phase which is one phase of the power lines is connected to the electrode H which is one end of the series connection of the three electrode pairs.

The electrode M, which is the other end of the series connection, is connected to the shell casing 51 of the compressor 50, and the shell casing 51 is connected to the ground potential point. The electrode H may be connected to the U phase or W phase of the power line of the inverter 36. The interelectrode voltages of the electrode pair 2b, the electrode pair 2c, and the electrode pair 2d are V _2b , V _2c , and V _2d , respectively.

  Furthermore, the wiring drawn out from each electrode pair is connected to the relay switch 4a. The relay switch 4 a can switch the electrode pair to be measured by a signal from the relay switch control unit 63, and selects one of the electrode pairs 2 b, 2 c, and 2 d and connects it to the voltage measuring device 15. 6A and 6B show a state in which the electrode H and the electrode I of the electrode pair 2b are connected to the voltage measuring device 15. FIG. The determination unit 64 switches the relay switch 4a, stores the measurement result in the storage unit 65, compares the measurement result, and the like, and compares the interelectrode voltage and detects the difference between the interelectrode voltages.

Hereinafter, in the third embodiment, a procedure for detecting the oil level position by comparing the capacitance, that is, the voltage between the electrodes of the electrode pair will be described. FIG. 7 is a flowchart showing the procedure. In the flowchart, step S0 is a step of comparing the interelectrode voltage _V2b with the interelectrode voltage _V2c .

From step S0, if there is a significant difference between the interelectrode voltage _V2b and the interelectrode voltage _V2c , the process proceeds to step S1, and if there is no significant difference, the process proceeds to step S2. Step S1 is a step in which time measurement is started when it is determined that the liquid level is between 2b and 2c, and measurement in step S0 is started again after the measurement time interval has elapsed.

Step S2 is a step for comparing the interelectrode voltage _V2c and the interelectrode voltage _V2d. If there is a significant difference, the process proceeds to step S3. If there is no significant difference, the process proceeds to step S4. Step S3 is a step in which it is determined that the liquid level is between 2c and 2d, and the process proceeds to step S5. Step S4 is a step in which the liquid level is determined to be below 2d, and the process proceeds to step S6.

  Step S5 is a step of performing an operation for recovering the amount of refrigerating machine oil. After step S5, time measurement is started, and after the measurement time interval has elapsed, the process returns to step S0 and starts measurement. In step S6, the apparatus is stopped. After that, it is a step of performing an inspection and an operation for recovering the amount of refrigeration oil. In step S6, time measurement is started after the apparatus is in a state where it can be normally operated, and after the measurement time interval has elapsed, the process returns to step S0 to start measurement again.

The operation of the apparatus will be described below. First, a signal is sent from the determination unit 64 to the relay switch control unit 63, and the voltage measuring device 15 is connected to the electrode pair 2b by operating the relay switch 4a. The voltage V _2b between the electrodes of the electrode pair 2b is detected by the voltage measuring device 15 and temporarily stored in the storage unit 65. When the detection is completed, the relay switch control unit 63 operates the relay switch 4a to disconnect the connection with the electrode pair 2b.

Subsequently, the relay switch control unit 63 receives the signal from the determination unit 64 and connects the voltage measuring device 15 to the electrode pair 2c. The interelectrode voltage V _2c detected by the voltage measuring device 15 is compared with the interelectrode voltage V _2b stored in the storage unit 65 by the determination unit 64. This is step S0. When there is a significant difference between the interelectrode voltage _V2b and the interelectrode voltage _V2c , it is determined that the oil level is between the electrode pair 2b and the electrode pair 2c, as in the first embodiment.

  In this case, it is determined that the oil level is within the appropriate range, the process proceeds to step S1, and the measurement of the oil level ends here. Whether there is a significant difference can be determined, for example, by providing a threshold value in advance and determining that there is a significant difference when the difference in voltage between the electrodes exceeds the threshold value.

  The relay switch control unit 63 operates the relay switch 4a to disconnect from the electrode pair 2c. In this case, since the oil level is in the normal range, an operation for recovering the oil level is not performed. Thereafter, time measurement is started, and after the measurement time interval elapses, the process returns to step S0 and starts measuring in step S0.

If it is determined that there is no significant difference between the inter-electrode voltage V _2b and the inter-electrode voltage V _2c, the flow proceeds to step S2. First, the interelectrode voltage V _2c is stored in the storage unit 65. Subsequently, the signal from the determination unit 64 is received, and the relay switch 4a is switched by the relay switch control unit 63 to measure the interelectrode voltage of the electrode pair 2d.

Determination unit 64 performs inter-electrode voltage _{V 2d} electrode pair 2d, a comparison between the inter-electrode voltage _{V 2c.} This is step S2. If there is a significant difference between the inter-electrode voltage V _2c and the inter-electrode voltage V _2d, the process proceeds to step S3, the oil level is determined to be between the electrode pairs 2c and the electrode pair 2d oil level measurement is completed. In this case, the operation proceeds to step S5 and the oil level is recovered by controlling the cooling device or the like.

  It is preferable that the oil level recovers slightly below the electrode pair 2b. Time measurement is started after the oil level is restored to the proper level. Thereafter, after the measurement time interval elapses, the process returns to step S0 to start the measurement of step S0.

In step S2, when there is no significant difference between the interelectrode voltage _V2c and the interelectrode voltage _V2d , it is determined that the oil level is below the electrode pair 2d, the process proceeds to step S4, and the process further proceeds to step S6.

  In some of the patterns shown in FIG. 7, when time measurement is started, after a certain time has passed, the process returns to the step of comparing the voltage between the electrode pair 2b and the electrode pair 2c in step S0. Here, the fixed time is the measurement time interval of FIG. 7, and is preferably 1 second to several minutes during which the amount or state of the refrigerating machine oil is considered not to change significantly.

  In step S4, when the oil level is below the electrode pair 2d, it was confirmed that the oil level 59 was operated in a state not in the proper range. As an example of handling in this case, the apparatus is stopped and inspected before the operation for recovering the oil amount of the refrigerating machine oil 56 is performed as shown in step S6.

  Thereafter, an operation for recovering the oil amount of the refrigerator oil 56 may be performed, and the operation may be resumed. After performing the operation for recovering the oil amount in step S6, time measurement is started, and after the measurement time interval has elapsed, the process returns to step S0 and the measurement in step S0 is started.

  Moreover, you may perform maintenance operation, such as performing the operation | movement which recovers an oil surface until refrigeration oil is fully supplied inside a compressor as needed. In this case, the oil level described in the third embodiment may be detected to manage the recovery amount of the refrigerating machine oil 56 so that the oil level does not exceed the electrode pair 2b and falls outside the proper range.

  As an example of specific management, when it is determined that it is between the electrode pair 2c and the electrode pair 2d as shown in S3, an operation of recovering the oil level is performed in step S5. The recovery amount of the refrigerating machine oil in step S5 is in a range not exceeding the electrode pair 2b.

  In addition, when it is determined that the oil level is below the electrode pair 2d as in S4, an operation for recovering the refrigerating machine oil in a larger amount than in step S5 is performed in step S6. Also in this case, the recovery amount of the refrigerating machine oil is in a range not exceeding the electrode pair 2b. As described above, it is preferable to perform management such as changing the operation time for recovering the amount of the refrigerating machine oil in accordance with the detected position of the oil level.

  In the third embodiment, a case where three electrode pairs, one near the upper limit of the appropriate range, one near the lower limit, and one slightly above the lower limit, are arranged. As another example of arrangement, one is provided slightly below the upper limit, and the measurement is performed when the operation for recovering the amount of refrigerating machine oil is performed, until the amount of refrigerating machine oil reaches between the upper limit and the upper limit slightly. An oil amount recovery operation may be performed.

  As in the third embodiment, a method of temporarily storing measured data and comparing it with the next measured value is effective when there are a large number of electrode pairs. Although the case where the number of electrode pairs is 3 has been described in the third embodiment, the oil level may be measured more finely by setting the number of electrode pairs to 4 or more.

  Although FIG. 6A showing the third embodiment does not have a voltage dividing circuit, even if the measured interelectrode voltage passes through the voltage dividing circuit and then is connected to the relay switch as in the second embodiment. good. If the voltage dividing circuit is provided in this way, the voltage between the electrodes is stepped down by the voltage dividing circuit and then input to the voltage measuring device 15, so that the withstand voltage of the voltage measuring device can be lowered. Further, for example, if a configuration like the voltage dividing circuit 22a of FIG. 5A is provided and the resistance value of the voltage dividing circuit is variable, there is an effect that calibration between the electrode pairs can be performed.

  Three electrode pairs were connected in series, the inverter power line was connected to one end of the series connection, and the other end was connected to the ground potential point. For this reason, the voltage between the electrodes of the electrode pair can be made larger than noise existing around, for example, noise caused by the drive power supply, AC power supply, etc. of the compressor. Thereby, the SN ratio is high, and the measurement of the inter-electrode voltage and the detection of the liquid surface position can be performed with high accuracy and high reliability.

Embodiment 4 FIG.
In the fourth embodiment, one phase of the inverter power lines is connected to one end of a plurality of electrode pairs connected in series, and another phase of the inverter power lines is connected to the other end. Here, the inverter is also called an inverter circuit.

  FIG. 8A and FIG. 8B are diagrams showing the configuration of the fourth embodiment. The configuration of the inverter and the operation of the compressor are the same as in FIG. In FIG. 8A and FIG. 8B, the three-phase AC power supply 31 is connected to the rectifier circuit 33.

  The rectifier circuit 33, the booster circuit 34, and the smoothing capacitor 35 constitute a converter circuit 32. Both ends of converter circuit 32 are connected to N bus LBn and P bus LBp of inverter 36, and three-phase power lines LPv, LPu, LPw are connected to compressor 50 from inverter 36.

  The compressor 50 includes a shell casing 51 and a shell inner wall 51 a, and also includes a motor 54 including a stator 57 and a rotor 58. The motor 54 drives a volume compressor 55, and refrigeration oil 56 is used for the compressor. The refrigeration oil is stored inside the compressor below the oil level 59, and the oil level 59 has an appropriate range 200. The compressor includes a refrigerant suction port 52 and a discharge port 53. In the fourth embodiment, the shell casing 51 corresponds to a liquid storage container.

  Also in the fourth embodiment, the converter circuit, the inverter circuit, the compressor, the liquid amount detection device, and the like constitute the cooling device 500. The cooling device 500 includes a refrigerant circuit (not shown), a heat exchanger (not shown), and the like depending on the application.

The liquid amount detection device 1 includes a series circuit 7 and a detection circuit unit 6. The detection circuit unit 6 includes a voltage measurement device 15 and a comparison circuit 16. The comparison circuit 16 outputs the result of comparing the voltage between the electrodes. Specifically, the difference between the interelectrode voltage _V2b and the interelectrode voltage _V2c or the ratio between the two is output. The series circuit 7 includes an electrode pair 2b, an electrode pair 2c, and a conductor 401d. The electrode pair 2b includes an electrode H and an electrode I.

  The electrode pair 2c includes an electrode J and an electrode K. In this case, the electrode pair 2b and the electrode pair 2c are arranged at different positions in the vertical direction inside the compressor or inside the shell casing.

  Moreover, the electrode I which comprises the electrode pair 2b, and the electrode J which comprises the electrode pair 2c are connected by the connection line which is the conductor 401d. That is, two electrodes constituting different electrode pairs are connected in series by being connected by a conductor.

  In order to clearly indicate the reference numerals, a series circuit is separately illustrated in FIG. In the fourth embodiment, the U phase, which is one of the three phase power lines of the inverter, is connected to the electrode H which is one end of the electrode pair 2b and the electrode pair 2c connected in series. In addition, a W phase that is one phase different from the U phase among the power lines of the inverter was connected to the electrode K that is the other end of the electrode pair connected in series. The electrode K is not connected to the ground potential point, and the shell casing 51 is connected to the ground potential point.

  The U-phase, which is one phase of the inverter power line, and the W-phase, which is one phase of the inverter power line, are connected to both ends of the electrode pair 2b and the electrode pair 2c that are connected in series. Therefore, compared to the electrical noise caused by the driving power supply of the compressor generated in the surroundings, the interelectrode voltage of each installed electrode pair is compared and the interelectrode voltage that is a signal is increased when detecting the difference between the electrodes. Can be. Thereby, the liquid quantity with a high SN ratio can be detected. In addition, the liquid level can be detected with high accuracy.

  In the configuration of the first embodiment, the fluctuation component of the center potential of the inverter is superimposed on the output voltage of the inverter power line. The center potential of the inverter is a change in potential difference between the N bus line or P bus line of the inverter and the ground potential point, and often varies with the frequency of the AC power supply.

  Therefore, in the case of the first embodiment, the potential of the power line is obtained by superimposing the fluctuation component of the center potential of the frequency of the AC power supply on the fluctuation due to switching of the inverter, and this fluctuation may affect the measurement.

  On the other hand, when the line potential of the inverter power line is applied to both ends of the series circuit 7 which is a plurality of electrode pairs connected in series as shown in FIG. 8A and FIG. Since it is not affected by fluctuations in the center potential, there is an effect that highly accurate measurement is possible. Although the case where there are two electrode pairs has been described in the present embodiment, even when the number of electrode pairs is three or more, highly accurate measurement that is hardly affected by the center potential can be performed.

Embodiment 5. FIG.
In the fifth embodiment, a power line of an inverter is connected to one end of a series circuit that is a plurality of electrode pairs connected in series, and a bus of the inverter is connected to the other end. FIG. 9A and FIG. 9B are diagrams showing the configuration of the fifth embodiment. Since the operation of the inverter 36 and the operation of the compressor 50 are the same as those in the first embodiment, a description thereof will be omitted. In the fifth embodiment, the shell casing 51 corresponds to a liquid storage container.

  9A and 9B, the three-phase AC power supply 31 is connected to a rectifier circuit 33. The rectifier circuit 33, the booster circuit 34, and the smoothing capacitor 35 constitute a converter circuit 32. Both ends of converter circuit 32 are connected to N bus LBn and P bus LBp of inverter 36, and three-phase power lines LPv, LPu, LPw are connected to compressor 50 from inverter 36. Here, the inverter is also called an inverter circuit.

  Also in the fifth embodiment, the converter circuit, the inverter circuit, the compressor, the liquid amount detection device, and the like constitute the cooling device 500. The cooling device 500 includes a refrigerant circuit (not shown), a heat exchanger (not shown), and the like depending on the application.

  The compressor 50 includes a shell casing 51 and a shell inner wall 51 a, and also includes a motor 54 including a stator 57 and a rotor 58. The motor 54 drives a volume compressor 55, and refrigeration oil 56 is used for the compressor. The refrigerating machine oil is stored below the oil level 59 inside the compressor, and the oil level 59 has an appropriate range 200. The compressor includes a refrigerant suction port 52 and a discharge port 53.

The liquid amount detection device 1 includes a series circuit 7 and a detection circuit unit 6. The detection circuit unit 6 includes a voltage measurement device 15 and a comparison circuit 16. The comparison circuit 16 outputs the result of comparing the voltage between the electrodes. Specifically, the difference between the interelectrode voltage _V2b and the interelectrode voltage _V2c or the ratio between the two is output. The series circuit 7 includes an electrode pair 2b and an electrode pair 2c.

  The electrode pair 2b includes an electrode H and an electrode I. The electrode pair 2c includes an electrode J and an electrode K. In this case, the electrode pair 2b and the electrode pair 2c are disposed inside the shell casing or the compressor, and their positions are different in the vertical direction. Further, they are arranged apart from each other.

  In order to clarify the reference numerals, the series circuit 7 is shown in FIG. The electrode pair 2b and the electrode pair 2c arranged inside the compressor are connected in series. The electrode pair 2b, the electrode pair 2c, and the conductor 401e which is a connecting line therebetween constitute the series circuit 7. The electrode I constitutes an electrode pair 2b, the electrode J constitutes an electrode pair 2c, and the electrode I and the electrode J constitute different electrode pairs.

  That is, the conductor 401e connects between two electrodes that constitute different electrode pairs to form a series connection, thereby forming a series circuit 7 that is a plurality of electrode pairs connected in series. Since the operation of the detection circuit unit 6 is the same as that of the first embodiment, the description thereof is omitted.

  The electrode H which is one end of the series circuit 7 is connected to the U phase which is one phase of the power lines of the inverter. The electrode K which is the other end of the series circuit 7 is connected to the N bus of the inverter. The power line connected to the electrode H may be a V phase or a W phase. The bus connected to the electrode K may be a P bus LBp.

  In the fifth embodiment, the U phase, which is one phase of the inverter power lines, and the N bus of the inverter are connected to both ends of the electrode pair 2b and the electrode pair 2c connected in series. Compared to electrical noise caused by driving a compressor that is expected to occur in the surroundings, it is possible to increase the interelectrode voltage that becomes the signal output, so the interelectrode voltage of the installed electrode pair is compared. It is possible to reduce the influence of noise when detecting the voltage difference between the electrodes.

  In addition, when PWM control is performed, there is an advantage that the impedance of the detection circuit does not need to be particularly high because the frequency is relatively high. From the above, it is possible to measure the voltage between the electrodes with high accuracy and high reliability, and to detect the oil level with high accuracy.

  In the fifth embodiment, one phase of the power lines is connected to one end of a plurality of electrode pairs. Further, the N bus of the inverter is connected to the other ends of the plurality of electrode pairs. Therefore, the AC power supply that applies a voltage to both ends of the electrode pair 2b and the electrode pair 2c connected in series is the potential of the inverter power line (the U phase in the case of Embodiment 5) with respect to the N bus, This is the voltage across the U-phase N-side element (collector-emitter voltage).

  Since the voltage across the U-phase N side element of the inverter is not affected by the fluctuation of the center potential of the inverter, the SN ratio can be increased. Therefore, as in the fourth embodiment, there is an effect that the reliability is high and the detection can be performed with high accuracy.

  Further, when the potential of the control system of the inverter is the N bus potential, the reference potential of the control system and the electrode pair does not fluctuate, so that an isolation amplifier is not required in the detection circuit, and the circuit configuration can be simplified.

Embodiment 6 FIG.
In the sixth embodiment, a series circuit is provided in the accumulator that supplies the refrigerant to the compressor. FIG. 10A and FIG. 10B are diagrams showing the configuration of the sixth embodiment. In the sixth embodiment, the accumulator 70 corresponds to a liquid storage container.

  Also in the sixth embodiment, the converter circuit, the inverter circuit, the compressor, the liquid amount detection device, and the like constitute the cooling device 500. The cooling device 500 includes a refrigerant circuit (not shown), a heat exchanger (not shown), and the like depending on the application.

  10 (a) and 10 (b), the inverter 36 and the compressor 50 are connected by three-phase power lines LPv, LPu, LPw, and the compressor 50 includes a shell casing 51 and a shell inner wall 51a. Yes. Further, a motor 54 composed of a stator 57 and a rotor 58 and a volume compressor 55 driven by the motor 54 are provided. Further, it has a refrigerant inlet 52 and a refrigerant outlet 53. Refrigerating machine oil 56 is stored in the compressor. Here, the inverter is also called an inverter circuit.

  The accumulator 70 stores the refrigerant 71 below the refrigerant liquid level 72 inside the accumulator 70, and includes a glass terminal T2. Further, the accumulator 70 is provided with a series circuit 7 of the liquid amount detection device 1a, and the series circuit 7 includes an electrode pair 2b and an electrode pair 2c as shown in FIG. 10B. The electrode pair 2b includes an electrode H and an electrode I. The electrode pair 2 c includes an electrode J and an electrode K.

  Electrode I and electrode J are connected by conductor 401f. That is, the electrode I constituting the electrode pair 2b and the electrode J constituting the electrode pair 2c are connected by the conductor 401f. The liquid amount detection device 1a includes a detection circuit unit 6a, and the detection circuit unit 6a includes a voltage dividing circuit 22a, an insulation amplifier 24a, an addition circuit 29, and a voltage detection circuit 20c.

  In FIG. 10A, the compressor 50 is operated by a motor 54 driven by an inverter 36. Since the operations of the compressor 50 and the inverter 36 are the same as those in the first embodiment, the description thereof is omitted. An accumulator 70 is connected to the suction port 52 for supplying the refrigerant to the compressor via a pipe.

  In the accumulator 70, both a gaseous refrigerant and a liquid refrigerant are stored. Among these, gaseous refrigerant is supplied to the compressor. Even when a small amount of refrigerating machine oil is mixed in the refrigerant, the voltage between the electrodes of the electrode pair above the refrigerant liquid level 72 in the vertical direction and the electrode pair below the refrigerant liquid level 72 in the vertical direction are compared. The difference between the two can be detected.

  The configuration of the series circuit 7 will be described. Two pairs of electrodes 2b and 2c connected in series are provided at different heights inside the accumulator. That is, the electrode pair 2b and the electrode pair 2c are disposed inside the accumulator and are installed at different positions in the vertical direction.

  A series circuit 7 is formed by connecting the electrode pair 2b and the electrode pair 2c in series. The position of the electrode pair 2b is slightly below the upper limit of the coolant level, and the position of the electrode pair 2c is slightly above the lower limit of the coolant level. The shape of the electrode pair is a parallel plate, and the plate portion is arranged in parallel with the liquid surface.

  The casings of the compressor 50 and the accumulator 70 are connected to a ground potential point. A U-phase power line that is one of the power lines of the inverter is connected to an electrode H that is one end of an electrode pair connected in series. The electrode K which is the other end of the electrode pair connected in series is connected to the ground potential point by being connected to the housing of the accumulator 70.

  The refrigerant liquid level 72 can be detected by the same method as when the position of the oil level in the second embodiment is detected.

  10A and 10B includes a voltage dividing circuit 22a, an insulation amplifier 24a, an adding circuit 29, and a voltage detecting circuit 20c. The liquid amount detection device 1a is composed of a series circuit 7, a detection circuit unit 6a, a connection line to a ground potential point, and the like. The detection circuit units in FIGS. 10A and 10B are configured in the same manner as the circuit configurations in FIGS. 5A and 5B, and the included components and operations are the same. .

  Similar to the circuit configuration of the second embodiment, the voltage difference between the electrodes 2b and 2c is detected, or the presence or absence of a difference is detected by reversing and adding one of the signs. Judge whether it is in the proper range.

The interelectrode voltage _V2b and the interelectrode voltage _V2c are dropped to a voltage suitable for detection by the voltage dividing circuit 22a, and input to the adding circuit 29 through the insulation amplifier 24a. The voltage detection circuit 20c determines whether or not there is a difference in the added value, and determines whether or not the liquid level of the refrigerant is within an appropriate range.

  As will be described later in Embodiment 6, the configuration of the present invention is not limited to a compressor that is a load device driven by an inverter, but is also used to detect the state of liquid such as accumulators and reservoir tanks used in refrigerators and cooling devices. Can be used for In this case, the liquid storage container is an accumulator, a reservoir tank or the like, and the load device driven by the inverter is a compressor.

  In addition, the accumulator and the reservoir tank are often provided near the compressor, and electrical noise generated by driving the compressor is likely to be noise in liquid level detection. Further, since electricity is often supplied from a common AC power source, the switching frequency of the inverter PWM control is often higher than the AC frequency of the common AC power source. Also, it is often easy to draw wiring from an inverter that drives the compressor.

  That is, the measurement of the liquid surface position and the liquid state performed by connecting the power line of the inverter is not limited to the equipment on which the load device driven by the inverter is mounted. For example, the present invention can also be applied to a liquid storage container that stores liquid in order to supply the liquid to equipment equipped with a load device driven by an inverter.

  In the case of the present embodiment, since the liquid storage container is near the inverter, electric noise is often generated by driving the load device by the inverter. In such a case, since the voltage of the power line of the inverter is applied between the electrodes of the electrode pair, it is possible to detect a signal having a larger voltage value than noise.

  In addition, when an inverter using PWM control is used, the impedance of the electrode pair can be lowered because the signal is a high frequency signal. As a result, there is an advantage that the interelectrode voltage can be measured, the interelectrode voltage can be compared, and the difference can be detected with little error.

Embodiment 7 FIG.
The seventh embodiment uses a single-phase inverter. Furthermore, the present invention can be applied not only to a full-bridge inverter but also to other types of inverters such as a half-bridge inverter.

  The circuit configuration between the three-phase AC power supply 31 and the full bridge inverter 37 and the configuration of the liquid amount detection device 1 are the same as those in the first embodiment, and detailed description thereof is omitted.

  11A and 11B, the three-phase AC power supply 31 is connected to a rectifier circuit 33. The rectifier circuit 33, the booster circuit 34, and the smoothing capacitor 35 constitute a converter circuit 32. Both ends of the converter circuit 32 are connected to the N bus LBn and the P bus LBp of the full bridge inverter 37, and the two-phase power lines LPu and LPv of the full bridge inverter 37 are connected to the load 154. Here, the inverter is also called an inverter circuit.

  The load device 150 includes a load 154 and a liquid storage container 151, and the liquid 158 is stored below the liquid level 155 inside the liquid storage container 151. The liquid storage container 151 is provided with a glass terminal T <b> 2 and further includes a series circuit 7 constituting the liquid amount detection device 1.

  The series circuit 7 includes an electrode pair 2b and an electrode pair 2c as shown in FIG. The electrode pair 2b has an electrode H and an electrode I. The electrode pair 2c has an electrode J and an electrode K. The electrode I constituting the electrode pair 2b and the electrode J constituting the electrode pair 2c are connected by a conductor 401g, the electrode pair 2b and the electrode pair 2c are connected in series, and a plurality of electrode pairs are connected in series.

The detection circuit unit 6 constituting the liquid amount detection device 1 includes a voltage measurement device 15 and a comparison circuit 16. Comparison circuit 16 outputs a comparison result by comparing the inter-electrode voltage V _2c of the inter-electrode voltage V _2b and the electrode pair 2c electrode pair 2b. Specifically, the ratio or difference between the interelectrode voltage _V2b and the interelectrode voltage _V2c is output.

  The U-phase LPu and the V-phase LPv, which are two-phase power lines, are connected to the load 154 from the full bridge inverter 37, and the load device 150 is driven. In the case of a three-phase inverter, there are three power lines, U-phase, V-phase, and W-phase, but in the case of the single-phase inverter in FIG. 11A, there are two power lines, U-phase and V-phase. The motor is often driven in three phases. The load device 150 may be a motor, but may be an induction heater or an ozonizer, for example.

  FIG. 11A and FIG. 11B illustrate the case where the load device is driven by the full bridge inverter 37. However, it is not always necessary to use the power line for driving the load device for detecting the liquid amount, and an AC voltage generated for boosting or stepping down in the power conversion circuit may be used for detecting the liquid amount. In this case, the liquid amount detection device does not have to be provided inside the load device driven by the inverter, and the present invention can be applied even if it is outside.

  As in the first embodiment, the interelectrode voltages of the two electrode pairs are measured by the provided voltage measuring devices 15 and compared by the comparison circuit 16 to know the difference in capacitance and the value of capacitance. Can do. Further, the liquid amount detection device using the voltage dividing circuit shown in FIG. 5 can be applied to a single-phase full-bridge inverter.

  Further, one phase of the power lines of the single-phase full-bridge inverter is connected to one end of the series circuit similarly to FIGS. 9A and 9B, and the other end is connected to the single-phase full-bridge inverter. It can also be connected to a bus. Furthermore, a liquid amount detection device that detects the position of the liquid surface by comparing the voltage between the electrodes of the installed electrode pair and detecting the difference can be configured. In this case, the influence of fluctuations in the three-phase AC power supply can be reduced, which is preferable.

  In order to clearly indicate the reference numerals, the series circuit 7 is illustrated in FIG. Inside the liquid storage container 151, the electrode pair 2b and the electrode pair 2c are installed at different heights parallel to the liquid surface.

  In the present embodiment, the inter-electrode voltage between the electrode pair immersed in the liquid and the electrode pair not immersed in the liquid is compared, and the difference between the two is detected to detect the position of the liquid surface in the vertical direction. .

  Since the power line of the inverter is connected to one end of the series circuit, a voltage higher than the noise generated by the power source that drives the load device generated around the inverter can be applied to the electrode pair. Therefore, a signal larger than noise can be detected, and detection with high accuracy can be performed without being affected by noise.

Embodiment 8 FIG.
In the eighth embodiment, detection is performed while the compressor 50 is stopped. The background for understanding the operation and effects of the eighth embodiment will be described. When the compressor, such as an outdoor unit of an air conditioner, is placed in a low temperature state, there may be a phenomenon that the refrigerant gathers in the compressor and the concentration of the refrigerant in the refrigeration oil increases. This phenomenon is known as a refrigerant stagnation phenomenon. Since the outside air is low temperature, the air conditioner is often used as a heater.

  It is known that when an air conditioner, a refrigerator, or the like is operated in a state in which a stagnation occurs, an abnormality in the refrigerant concentration in the refrigerator oil adversely affects the operation of the compressor. Therefore, before the operation of the apparatus is started after the compressor is stopped for a certain period of time in an environment of a certain temperature or less, energization is performed for a certain period of time in order to eliminate the refrigerant stagnation phenomenon. Or the installation for always keeping the temperature of an apparatus above fixed temperature etc. has been performed. In the case of Embodiment 8, these air conditioners, refrigerators, etc. are also called cooling devices.

  In the eighth embodiment of the present invention, it is possible to detect the concentration of the refrigerant in the refrigerating machine oil without adversely affecting the compressor in a state where there is a high possibility that the stagnation phenomenon will occur. That is, it is possible to detect the voltage between the electrodes of the electrode pair immersed in the refrigerating machine oil inside the compressor shell with the compressor stopped. The value of the electrostatic capacity can be obtained from the voltage between the electrodes, and the concentration of the refrigerant in the refrigerating machine oil can be detected.

  Further, it is possible to determine whether or not the stagnation phenomenon occurs based on the detected density, and to take measures to eliminate the stagnation phenomenon described above. An example of the specific configuration, operation, and effect of the eighth embodiment will be described below.

  The configuration of the eighth embodiment is the same as that of the liquid amount detection device of the third embodiment shown in FIGS. 6 (a) and 6 (b). That is, the refrigerant concentration in the refrigerating machine oil is measured by measuring the capacitance or the change in the capacitance using the liquid amount detection device.

  In the liquid amount detection device according to the third embodiment shown in FIGS. 6A and 6B, the device is stopped in a situation where a stagnation phenomenon may occur. If no voltage is applied to the power line of the inverter 36 in a state where the compressor stops the compression operation, the signal of the liquid amount detection device 1b cannot be acquired. In order to perform the measurement, the compressor must be stopped while the inverter 36 applies a voltage to the power line. In the eighth embodiment, the shell casing 51 corresponds to a liquid storage container. Here, the inverter is also called an inverter circuit.

  Therefore, in a state where the compressor 50 stops the compression operation, the inverter 36 applies a voltage having a switching frequency higher than that during the compression operation to the compressor 50 and performs energization. Restraint energization is a method of energizing the winding of the motor 54 of the compressor under the condition that the compressor 50 does not move. For example, as a specific method in WO2014 / 188866, a method for setting the carrier frequency of the inverter 36 to a frequency higher than usual is described.

While applying a high frequency voltage by restraining energized, the inter-electrode voltage V _2b of the inter-electrode voltage V _2d and the electrode pair 2b of the electrode pairs 2d measure the voltage measuring device 15, calculates the capacitance of comparing the two V _2d To do. The refrigerant concentration is detected based on a conversion table that correlates between the concentration of the refrigerating machine oil and the capacitance stored in the storage unit 65 in advance.

Further, the ratio of the inter-electrode voltage V _2b of the inter-electrode voltage V _2d and the electrode pair 2b of the electrode pairs 2d may be provided a certain threshold, are any normal time (stagnation phenomenon by the upper and lower and the threshold And when it is not normal (when a stagnation phenomenon occurs).

  Here, when the energization of the motor is restrained, the winding of the motor 54 is heated by energization to heat the refrigerating machine oil 56 in the compressor 50 where the stagnation phenomenon has occurred, and the refrigerant in the refrigerating machine oil is evaporated. There is an advantage that the state of the refrigerating machine oil can be brought close to normal and the stagnation phenomenon can be eliminated.

  While performing the energization with the compressor stopped, the detection of the capacitance and the refrigerant concentration is continued, the energization is performed until the refrigerant concentration falls to a value suitable for the operation of the compressor, and then the operation is started. This is advantageous because it has the effect of avoiding operation in a high concentration state.

  Here, although an example was shown about the detection of the refrigerant | coolant density | concentration in refrigerating machine oil, the quantity of refrigerating machine oil and the liquid level position of refrigerating machine oil can also be detected during a compressor stop. When detecting the refrigerant concentration, if the amount of refrigerating machine oil is kept within the proper range, the entire electrode pair is below the oil level and is completely immersed in the refrigerating machine oil and the electrode pair completely immersed in the refrigerating machine oil. It is preferable to measure the dielectric constant by comparison with a pair of electrodes that are out and in the air.

  An example is given below. In FIG. 6 (a) and FIG. 6 (b), it is assumed that the electrode pair 2b is on the oil surface and the space between the electrodes is not filled with refrigerating machine oil. Furthermore, it is assumed that the electrode pair 2d is completely immersed in the refrigerating machine oil. Under such circumstances, the capacitances of the electrode pair 2b and the electrode pair 2d are compared.

  Based on the above comparison, if the ratio between the two is within a certain range, it is determined that the stagnation phenomenon has not occurred. If the ratio between the two is out of a certain range, it is determined that the stagnation phenomenon has occurred. In order to determine the occurrence of the stagnation phenomenon by comparing the voltage between the electrodes of such an electrode pair, it is preferable to provide a criterion for determination in advance between the capacitance ratio and the presence or absence of the stagnation phenomenon. is there.

  Here, the method for detecting the stagnation phenomenon has been described by taking the configuration of FIGS. 6A and 6B as an example. However, even in the configuration of the first embodiment, the stagnation phenomenon can be detected by making the following preparations. it can.

  Preparation for detecting the stagnation phenomenon confirms that one of the electrode pairs is completely immersed in the refrigerating machine oil and the other is coming out of the refrigerating machine oil. Furthermore, by comparing the voltage between the electrodes outside the refrigerating machine oil and the electrode in the refrigerating machine oil, the ratio of the interelectrode voltage and the stagnation phenomenon can be detected so that the refrigerant concentration can be detected and detected. Establish a standard in advance. These are two.

  As described above, according to the eighth embodiment, the stagnation phenomenon in which the refrigerant concentration in the refrigerating machine oil increases is applied with a higher switching frequency voltage than during the operation of the compressor, and is less affected by noise than the conventional method. Can be detected.

  Further, since the compressor does not operate when performing detection, the compressor can be maintained without adversely affecting the compressor. Furthermore, since the liquid level position can be detected with high accuracy with respect to the amount of the refrigerating machine oil, there is an effect that the operation of the compressor can be kept comprehensively.

  In the conventional apparatus, since the SN ratio is low and the capacitance cannot be detected with high accuracy, the stagnation phenomenon before the start of operation cannot be detected with sufficient accuracy. Therefore, before the operation of the apparatus is started after the compressor 50 is stopped for a certain time in an environment of a certain temperature or lower, for example, restraint energization is performed for a certain time in order to eliminate the refrigerant stagnation phenomenon. Or the installation for always keeping the temperature of an apparatus above fixed temperature etc. has been performed.

  For this reason, there is a problem that it takes time until the operation is started after turning on the power to the apparatus, and there is a problem that costs are required for heat insulation. In addition, there is a problem that warm-up operation and heat insulation are necessary even for a compressor that does not cause a stagnation phenomenon.

  If the present invention is applied, since the power line of the inverter is connected to one end of the series circuit, it is possible to detect a signal having a higher voltage than electrical noise due to driving of the compressor. Further, according to the ninth embodiment, since the inverter is driven at a frequency higher than that in a state where a normal compressor is driven, the impedance of the electrode pair can be lowered, and the accuracy is high. It is possible to detect the refrigerant concentration with high reliability.

  From the above, by detecting the electrostatic capacity or the change in the electrostatic capacity using the liquid amount detection device of the present invention, it is possible to detect with high accuracy whether or not the stagnation phenomenon has occurred, and to reduce the time until the start of operation. Can be shortened. There are effects such as warm-up operation, equipment required for heat insulation, and energy saving. Furthermore, there is an effect that it is possible to avoid operating the compressor in a state where the warming-up operation or the heat retention is insufficient and the stagnation phenomenon occurs.

Embodiment 9 FIG.
In the ninth embodiment, the inverter that drives the load device is different from the inverter that is connected to the series circuit installed inside the liquid container provided in the load device. Here, the inverter is also called an inverter circuit.

  Specific examples of devices that are supplied with lubricating oil and are connected to an AC power supply include mechanical equipment to which a three-phase AC power supply is connected and equipment having a generator that is used when the AC power supply is stopped.

  12 (a) and 12 (b) are diagrams showing the configuration of the ninth embodiment. In FIG. 12A, the three-phase AC power supply 31 is connected to the rectifier circuit 33. The rectifier circuit 33, the booster circuit 34, and the smoothing capacitor 35 constitute a converter circuit 32.

  Both ends of converter circuit 32 are connected to N bus LBn and P bus LBp of inverter 36, and three-phase power lines LPv, LPu, LPw are connected to load device 150a from the inverter circuit. The converter circuit 32a and the inverter 36b are connected.

  The power lines LPv, LPu, LPw of the inverter 36b are connected to the load device 150b. The load device 150 b is connected to the oil tank 152 via a pipe 157, and the series circuit 7 that is a part of the liquid amount detection device 1 is provided inside the oil tank 152. In the ninth embodiment, the oil tank 152 corresponds to a liquid storage container.

  As shown in FIG. 12B, the series circuit 7 includes an electrode pair 2b and an electrode pair 2c. Furthermore, the electrode pair 2b has an electrode H and an electrode I, and the electrode pair 2c has an electrode J and an electrode K. Signals from the electrode pair 2b and the electrode pair 2c are drawn out of the oil tank 152 from the glass terminal T2. The detection circuit unit 6 includes a voltage measurement device 15 and a comparison circuit 16.

  12 (a) and 12 (b), the three-phase inverter 36 receives power from the three-phase AC power supply 31, and drives the load device 150a by applying a voltage to the load device 150a via the power line. On the other hand, the inverter 36b receives power from the three-phase AC power supply 31 and drives the load device 150b through the power line.

  Oil 156 that serves as lubricating oil is stored in the oil tank 152, and the oil 156 is supplied to the load device 150 b via the pipe 157. Further, in order to detect the amount of oil 156, the oil tank 152 is provided with an electrode pair 2b and an electrode pair 2c connected in series. The electrode H is connected to the U phase which is one phase of the power lines of the inverter 36.

  The electrode K is connected to the N bus of the inverter 36. The electrode pair 2b is positioned slightly below the upper limit of the appropriate range of the oil surface, the electrode pair 2c is positioned slightly above the lower limit of the appropriate range of the oil surface, and the electrode pair 2b and the electrode pair 2c are perpendicular to each other. Are spaced apart from each other. The electrode pair 2b and the electrode pair 2c may be arranged so as to be separated from each other as described above, but may not be separated as long as they are arranged at different positions in the vertical direction.

The voltage between the electrode pair 2 b and the electrode pair 2 c is measured by the voltage measuring device 15 provided in each electrode pair and compared by the comparison circuit 16. Comparison circuit 16 outputs a comparison result by comparing the inter-electrode voltage V _2c of the inter-electrode voltage V _2b and the electrode pair 2c electrode pair 2b. Specifically, the ratio or difference between the interelectrode voltage _V2b and the interelectrode voltage _V2c is output. The electrode pair 2b and the electrode pair 2c connected in series by the conductor 401h constitute a series circuit.

  In FIG. 12 (a) and FIG. 12 (b), the measurement can also be performed by connecting the power line of the inverter 36b to one end of the electrode pair 2b and the electrode pair 2c connected in series. However, there may be a case where the voltage of the inverter 36b is low and the SN ratio cannot be sufficiently increased with respect to the surrounding noise source. Or the frequency may be low and the impedance of the electrode pair 2b and the electrode pair 2c may not be sufficiently low. In such a case, better measurement is possible when the power line of the inverter 36 is connected.

  Thus, even if the liquid to be measured is not supplied to the device driven by the inverter, if there is an inverter device that can be connected to the periphery, it can be used to generate a signal by connecting the power line.

  In the case of FIG. 12A and FIG. 12B, one phase of the power line of the inverter 36 is connected in series with the electrode pair 2b and the electrode pair 2c, and the bus of the inverter 36 is connected to the electrode K. In this case, it is possible to reduce the influence of the fluctuation of the potential difference between the oil tank 152 and the ground potential point, which is preferable.

  Further, one phase of the power line can be connected to the electrode H, and one phase of another power line of the inverter 36 can be connected to the electrode K. It is also possible to connect a ground potential point to the electrode K. When the ground potential point is connected to the electrode K, the oil level of the oil tank 152 can be detected by monitoring the fluctuation between the reference potential of the detection circuit unit 6 and the bus potential of the inverter 36.

  The liquid to be measured is not limited to the oil described in the ninth embodiment, the refrigerant, and the refrigerator oil described in the other embodiments. The present invention can also be applied to other liquids such as cooling water (pure water).

  In the apparatus of FIG. 12A and FIG. 12B, measurement is performed in the noise generated from the inverter 36b, the load device 150a, the inverter 36, and the load device 150a. Since the inverter 36 is connected, it is possible to increase the signal obtained when comparing the voltage between the electrode pair 2b and the electrode pair 2c to detect the difference between the electrode voltages, and perform measurement with a high S / N ratio. The amount of liquid can be detected with higher accuracy.

  In the eighth embodiment, since refrigeration oil is indispensable for the operation of the apparatus and a stagnation phenomenon may occur, it is necessary to perform detection in a state where the apparatus is not operating. Therefore, restraint energization is performed when detecting the stagnation phenomenon.

  On the other hand, in FIGS. 12A and 12B, the device driven by the inverter used for detection can operate regardless of the state of the liquid to be detected. There is an advantage that there is no need to devise.

  Therefore, the measurement is not limited to the case where the inverter driving the device is not suitable for the measurement of the voltage between the electrodes, and the power line of the inverter of another device may be connected to the electrode and the measurement may be performed in a state where the device is not operating.

  As described above, according to the ninth embodiment, even if the power supply device that drives the load device is unsuitable for measurement, if there is an inverter device that is suitable for measuring the voltage between electrodes and can be connected, the SN ratio is High, reliable and accurate measurements can be performed.

  In this case, it is possible to perform measurement even if the AC power supply is not shared, but as shown in FIGS. 12A and 12B, between the devices sharing the three-phase AC power supply 31 In the case of wiring with the, it is preferable because the influence of the fluctuation component of the three-phase AC power supply 31 can be reduced.

  The configuration of the embodiment described above can be used in combination as necessary.

1, 1a, 1b Liquid amount detection device, 2b, 2c Electrode pair, 4, 4a Relay switch, 5 Temperature detection unit, 6, 6a, 6b Detection circuit unit, 7 Series circuit, 10 control unit, 15 Voltage measurement device, 16 Comparison circuit 20, 20a, 20b, 20c Voltage detection circuit, 21 Voltage detection unit, 21a Low frequency filter, 22, 22a Voltage division circuit, 23, 23a, 23b Detection side rectification circuit, 24, 24a, 24b Insulation amplifier, 25 Amplifier, 26 Coaxial cable, 27 Twisted pair cable, 28 Filter capacitor, 29 Adder circuit, 31 Three-phase AC power supply, 32, 32a Converter circuit, 33, 33a Rectifier circuit, 34, 34a Booster circuit, 35, 35a Smoothing capacitor, 36, 36b inverter, 37 full bridge inverter, 50 compressor, 51 shell housing, 51a shell inner wall, 2 suction port, 53 discharge port, 54 motor, 55 volume compressor, 56 refrigerator oil, 57 stator, 58 rotor, 59 oil level, 60 voltage follower, 61 control circuit, 63 relay switch control unit, 64 judgment unit, 65 Storage unit, 70 Accumulator, 71 Refrigerant, 72 Refrigerant liquid level, 150, 150a, 150b Load device, 151 Liquid storage container, 152 Oil tank, 154 Load, 155 Liquid level, 156 Oil, 157 Piping, 158 Liquid, 200 Appropriate Range, 300, current waveform 301, inverter output waveform, 401, 401a, 401b, 401c, 401d, 401e, 401f, 401g, 401h conductor, 500 cooling device, C _2b , C _2c , C _2d capacitance, Cs floating Capacitance, H, I, J, K, L, M electrodes, LBn N bus, LBp P bus, Pu, LPv, LPw power lines, T2 glass _{terminal, V 2b, V 2c, V} 2d voltage between electrodes, S0, S1, S2, S3 , S4, S5, S6 step.

Claims (10)

A compressor driven by an inverter circuit to compress refrigerant and store refrigeration oil inside;
Each of the plurality of electrode pairs is installed at different positions in the vertical direction inside the compressor, and one electrode of the electrode pair and one electrode of the electrode pair and another electrode pair A series circuit in which the plurality of electrode pairs are connected in series by being connected by a conductor, one end is connected to one of the power lines of the inverter circuit, and the other end is connected to a ground potential point;
A detection circuit unit for detecting the position of the oil surface of the refrigerating machine oil by comparing the voltage between the electrodes of each electrode pair of the series circuit and detecting the difference between the voltage between the electrodes of each electrode pair;
A liquid amount detection device comprising: When the difference between the interelectrode voltages of the two electrode pairs in the series circuit is detected and the difference between the interelectrode voltages is greater than or equal to a predetermined threshold, the two in the vertical direction Detecting that the oil level is at a position between the electrode pair,
2. The liquid level detection device according to claim 1, wherein when the difference between the inter-electrode voltages is smaller than the threshold value, it is detected that the oil level is not present at a position between the two electrode pairs in the vertical direction. .   A voltage measuring unit that measures the voltage between the electrodes of the electrode pair, and a relay switch that switches a connection between each of the electrode pairs constituting the series circuit to be detected and the voltage measuring unit. The liquid amount detection apparatus according to claim 1 or 2, characterized in that   4. The liquid quantity detection device according to claim 1, wherein any one of the conductors constituting the series circuit is a reference potential of the detection circuit unit. 5.   5. The liquid amount detection device according to claim 1, wherein a calibration unit that calibrates an inter-electrode voltage of an electrode pair constituting the series circuit is provided in the detection circuit unit. A compressor that is driven by an inverter circuit having a plurality of phases of the power line, compresses the refrigerant, and stores refrigeration oil therein;
Each of the plurality of electrode pairs is installed at different positions in the vertical direction inside the compressor, and one electrode of the electrode pair and one electrode of the electrode pair and another electrode pair The plurality of electrode pairs are connected in series by being connected by a conductor, and the power of the phase different from that of the power line having one end connected to one of the power lines of the inverter circuit and the other end connected to the one end. A series circuit connected to the wire;
A detection circuit unit for detecting the position of the oil surface of the refrigerating machine oil by comparing the voltage between the electrodes of each electrode pair of the series circuit and detecting the difference between the voltage between the electrodes of each electrode pair;
A liquid amount detection device comprising: A compressor driven by an inverter circuit to compress refrigerant and store refrigeration oil inside;
Each of the plurality of electrode pairs is installed at different positions in the vertical direction inside the compressor, and one electrode of the electrode pair and one electrode of the electrode pair and another electrode pair A series circuit in which the plurality of electrode pairs are connected in series by being connected by a conductor, one end is connected to one of the power lines of the inverter circuit, and the other end is connected to the bus line of the inverter circuit;
A detection circuit unit for detecting the position of the oil surface of the refrigerating machine oil by comparing the voltage between the electrodes of each electrode pair of the series circuit and detecting the difference between the voltage between the electrodes of each electrode pair;
A liquid amount detection device comprising:   The cooling device provided with the liquid quantity detection apparatus of any one of Claim 1 to 7.   When the compressor stops the compression operation, the inverter circuit applies a voltage having a switching frequency higher than that during the compression operation to the series circuit, and the refrigerating machine oil among the electrode pairs constituting the series circuit. The electrostatic capacity of the electrode pair below the oil level is calculated based on the difference in voltage between the electrode pair above the oil level and the electrode pair below the oil level, and the concentration of the refrigerating machine oil The cooling device according to claim 8, wherein the concentration of the refrigerating machine oil is obtained based on a conversion table that associates the capacitance with the capacitance. A load device comprising a liquid container and driven by an inverter circuit;
Each of the plurality of electrode pairs has a plurality of electrode pairs and is installed at different positions in the vertical direction inside the liquid container, and one electrode of the electrode pair and one electrode of the electrode pair and another electrode pair A series circuit in which the plurality of electrode pairs are connected in series by being connected by a conductor, one end is connected to one of the power lines of the inverter circuit, and the other end is connected to a ground potential point;
A detection circuit unit for detecting the position of the liquid level inside the liquid container by comparing the voltage between the electrodes of each electrode pair of the series circuit and detecting the difference between the voltages between the electrodes of each electrode pair When,
A liquid amount detection device comprising:

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