WO2023157580A1 - Heat pump system, and method for controlling heat pump system - Google Patents

Abstract

[Problem] To provide a heat pump system that is capable of protecting a compressor and of estimating the state of a suction refrigerant highly accurately while curbing costs. [Solution] The invention comprises: a refrigerant circuit 1 that includes a compressor 10 and in which a refrigerant circulates; a temperature sensor 2 that measures the temperature of the refrigerant; a pressure sensor 3 that measures the pressure of the refrigerant; and a drive suppression-control device 4 that determines a reduction in the pressure of the refrigerant sucked into the compressor 10 on the basis of a measurement value of the temperature sensor 2 and a measurement value of the pressure sensor 3, and that performs control to suppress driving of the compressor 10. The drive suppression-control device 4: controls the driving of the compressor 10 by determining a reduction in the pressure of the refrigerant sucked into the compressor 10, from the measurement value of the temperature sensor 2, in a case where a predetermined first condition is established; and performs control to suppress the driving of the compressor 10 by determining a reduction in the pressure of the refrigerant sucked into the compressor 10, from the measurement value of the pressure sensor 3, in a case where a predetermined second condition different from the first condition is established.

Description

Heat pump system and control method for heat pump system

The present invention relates to a heat pump system and a heat pump system control method.

Conventionally, heat pumps are known in which the refrigerant continuously radiates heat and absorbs heat by circulating in refrigerant pipes while repeatedly condensing and evaporating, thereby cooling and warming indoor air. Such a heat pump is used not only as a refrigerator or an air conditioner installed in a building, but also as a vehicle air conditioner that is mounted on a vehicle to cool and heat the interior of the vehicle.

By the way, the heat pump is provided with a compressor for compressing the refrigerant. The compressor could be damaged. For this reason, as disclosed in Patent Document 1, for example, a method of controlling the driving of the compressor is adopted so that the pressure of the refrigerant sucked into the compressor, that is, the suctioned refrigerant pressure does not become a negative pressure. Specifically, in Patent Document 1, the suction refrigerant pressure is measured by a pressure sensor on the suction side, or the pressure state of the refrigerant is detected by estimating it from the measurement value of the pressure sensor on the discharge side, and the compressor is driven. Inhibitory control is described.

JP 2011-168071 A

However, depending on the operating mode of the compressor, there are cases where the compressor must be steadily operated under conditions that are extremely close to the atmospheric pressure, even though the pressure is in a region higher than the atmospheric pressure. In this case, the pressure sensor is required to measure and detect minute drops in refrigerant intake pressure (shift to negative pressure) with high accuracy relative to normal operation, so high measurement accuracy is required for the pressure sensor. be. However, the pressure sensor has a problem of basically poor responsiveness and accuracy at the time of measurement near the atmospheric pressure. In order to solve this problem, a pressure sensor capable of measuring with higher accuracy and higher response is required even in an environment near atmospheric pressure, which may lead to an increase in cost.

Therefore, the present invention provides a heat pump system and a control method for the heat pump system that can estimate the state of the sucked refrigerant with high accuracy while keeping costs down and protect the compressor.

A heat pump system according to an aspect of the present invention includes a compressor, a radiator, an expansion mechanism, and a heat absorber that are connected to each other by refrigerant pipes, and the compressor, the radiator, the expansion mechanism, and the heat absorber a refrigerant circuit in which refrigerant can circulate through the refrigerant pipe in the order of the vessel, a temperature sensor for measuring the temperature of the refrigerant, a pressure sensor for measuring the pressure of the refrigerant, and a pressure drop of the refrigerant sucked into the compressor and a drive suppression control device that suppresses and controls the compressor so as to suppress the driving of the compressor by determining the determining the pressure drop of the refrigerant sucked into the compressor from the measured value of the temperature sensor, suppressing and controlling the compressor, and satisfying a predetermined second condition different from the first condition; In this case, the pressure drop of the refrigerant sucked into the compressor is determined from the measured value of the pressure sensor, and suppression control is performed on the compressor.

In the above heat pump system, the first condition includes that the measured value of the temperature sensor is equal to or lower than a predetermined reference temperature, and the second condition is that the measured value of the temperature sensor is higher than the reference temperature. may also include increasing

The heat pump system further includes an environmental temperature sensor that measures the temperature of the environment in which the heat absorber is installed, and the first condition is that the measured value of the environmental temperature sensor is equal to or lower than a predetermined reference environmental temperature. and the second condition may include that the measured value of the environmental temperature sensor is higher than the reference environmental temperature.

The heat pump system is used as a vehicle air conditioner mounted on a vehicle. and an outdoor air heat absorption heating operation mode in which the refrigerant circulating in the refrigerant circuit functions as an outdoor heat exchanger that absorbs heat into the compressor through the vehicle heat recovery device without passing through the heat absorber. a mode switching control device capable of switching the circulation path of the refrigerant in the refrigerant circuit between the recovery heating operation mode and the mode switching control device, wherein the first condition is that the mode switching control device is in the outside air heat absorption heating operation mode. mode, wherein the second condition may include switching to the heat recovery heating operation mode by the mode switching control device.

In the heat pump system, the first condition is that the actual pressure of the refrigerant immediately before being sucked into the compressor during steady operation (hereinafter referred to as the actual pressure immediately before suction) is equal to or lower than a predetermined reference pressure. The second condition may include that the actual pressure immediately before suction during steady operation is greater than the reference pressure.

In the above heat pump system, the pressure sensor measures the pressure of the refrigerant immediately before being sucked into the compressor, and the drive suppression control device detects the actual pressure immediately before the suction from the pressure sensor. It may be estimated from measurements.

In the above heat pump system, when the second condition is satisfied, the drive suppression control device measures the degree of superheat of the refrigerant immediately before being sucked into the compressor by measuring the measured value of the temperature sensor and the pressure sensor. It may be calculated from the value, and the driving of the compressor may be controlled based on the degree of superheat.

A control method for a heat pump system according to an aspect of the present invention comprises a refrigerant circuit configured by a compressor, a radiator, an expansion mechanism, and a heat absorber, which are connected to each other by refrigerant pipes. A control method for a heat pump in which a refrigerant circulates in the order of an expansion mechanism and the heat absorber, comprising: a temperature measurement step of measuring the temperature of the refrigerant; a pressure measurement step of measuring the pressure of the refrigerant; and a drive suppression control step of determining a pressure drop of the refrigerant and performing suppression control so as to suppress the driving of the compressor, wherein a predetermined first condition is satisfied in the drive suppression control step. the pressure drop of the refrigerant sucked into the compressor is determined from the measured value of the temperature sensor, the compressor is inhibited and controlled, and a predetermined second condition different from the first condition is satisfied. When the condition is established, the pressure drop of the refrigerant sucked into the compressor is determined from the measured value of the pressure sensor, and the compressor is restrained and controlled.

According to the above heat pump system, etc., it is possible to estimate the state of the sucked refrigerant with high accuracy while keeping costs down, thereby protecting the compressor.

It is a mimetic diagram showing a heat pump system concerning a first embodiment of the present invention. (A) is a block diagram showing a hardware configuration of an ECU of the heat pump system of the first embodiment, and (B) is a block diagram showing a functional configuration of the ECU. 4 is a saturation curve showing characteristics of refrigerant circulating in the refrigerant circuit of the heat pump system of the first embodiment; It is a figure which shows the flow of the control method of the heat pump system of said 1st embodiment. 4 is a ph diagram showing the state of refrigerant circulating in the refrigerant circuit of the heat pump system of the first embodiment; FIG. It is a schematic diagram which shows the modification of the heat pump system of said 1st embodiment. It is a mimetic diagram showing a heat pump system concerning a second embodiment of the present invention. (A) is a block diagram showing the hardware configuration of an ECU of the heat pump system of the second embodiment, and (B) is a block diagram showing the functional configuration of the ECU.

[First Embodiment]
A heat pump system 100 according to the first embodiment of the present invention will be described below.
The heat pump system 100 cools or warms indoor air using a refrigerant. The place where the heat pump system 100 is installed is not particularly limited, but in the present embodiment, the heat pump system 100 is used in a vehicle air conditioner (air conditioner) that is mounted on a vehicle and performs cooling and heating of the vehicle interior. explain.

The heat pump system 100 as a vehicle air conditioner may be installed in a vehicle powered only by an internal combustion engine. It is suitable for vehicles such as difficult HEV (Hybrid Electric Vehicle) and EV (Electric Vehicle) that cannot be heated by exhaust heat of the internal combustion engine.

(overall structure)
As shown in FIG. 1, the heat pump system 100 includes a refrigerant circuit 1 in which refrigerant circulates, a temperature sensor 2 that measures the temperature of the refrigerant in the refrigerant circuit 1, a pressure sensor 3 that measures the pressure of the refrigerant in the refrigerant circuit 1, A drive suppression control device 4 that suppresses and controls the driving of the compressor 10 in the refrigerant circuit 1 based on the measured value of the temperature sensor 2 and the measured value of the pressure sensor 3 is provided.

(refrigerant circuit)
The refrigerant circuit 1 has a compressor 10, a first heat exchanger 11, an expansion mechanism 12, a second heat exchanger 13, and refrigerant pipes 14 connecting these to each other. In the heating operation mode, which will be described later, in the refrigerant circuit 1, the refrigerant circulates through the refrigerant pipes 14 through the compressor 10, the first heat exchanger 11, the expansion mechanism 12, and the second heat exchanger 13 in this order.
Here, in this embodiment, the case where "R134a" is used as the refrigerant will be described, but the type of refrigerant is not particularly limited, and may be, for example, R-1234yf.

(compressor)
The compressor 10 sucks and compresses the refrigerant from the upstream side of the refrigerant circuit 1 and discharges the refrigerant downstream as a high-temperature, high-pressure gas. Although the type of the compressor 10 is not particularly limited, for example, a piston-type or scroll-type electric compressor is adopted. An accumulator 15 that separates liquid from the refrigerant is provided upstream of the compressor 10 in the refrigerant circuit 1 .

(first heat exchanger)
The first heat exchanger 11 functions as a radiator in this embodiment. In the first heat exchanger 11 as a radiator, the refrigerant, which has been turned into a high-temperature, high-pressure gas by the compressor 10, is allowed to pass therethrough, and heat is released from the refrigerant, thereby cooling the refrigerant. Here, the first heat exchanger 11 is arranged in a device called HVAC (Heating Ventilation and Air-Conditioning) 20 provided in the vehicle. In the HVAC 20, the air A taken into the air flow path 22 by the blower 21 is heated by exchanging heat with the refrigerant in the first heat exchanger 11, and is supplied into the passenger compartment. That is, in this embodiment, the heat pump system 100 is operated in the heating operation mode for heating the interior of the vehicle.

(Expansion mechanism)
The expansion mechanism 12 includes an expansion valve, a capillary tube, and the like, and decompresses and expands the high-pressure refrigerant that has passed through the first heat exchanger 11 to produce a low-pressure refrigerant.

(Second heat exchanger)
The second heat exchanger 13 functions as a heat absorber in this embodiment. In the second heat exchanger 13 as a heat absorber, the refrigerant whose pressure has been reduced by the expansion mechanism 12 is allowed to pass therethrough to absorb heat and heat the refrigerant. Here, the second heat exchanger 13 is an outdoor heat exchanger that causes the refrigerant to absorb heat from outside air.
In the heat pump system 100, by switching the circulation path of the refrigerant in the refrigerant circuit 1 with a switching valve (not shown), the second heat exchanger 13 functions as a radiator and the first heat exchanger 11 functions as a heat absorber. An operation in the cooling operation mode is also possible, but illustration and detailed description are omitted.

(temperature sensor)
The temperature sensor 2 is provided in the refrigerant pipe 14 on the upstream side of the inlet of the compressor 10 (downstream side of the accumulator 15) so as to be able to measure the temperature of the refrigerant immediately before being drawn into the compressor 10.

(pressure sensor)
The pressure sensor 3 is provided in the refrigerant pipe 14 on the upstream side of the inlet of the compressor so as to be able to measure the pressure of the refrigerant immediately before being drawn into the compressor 10 . In this embodiment, a pressure/temperature sensor in which the temperature sensor 2 and the pressure sensor 3 are integrated is provided as the temperature sensor 2 and the pressure sensor 3 . In this pressure/temperature sensor, the temperature and pressure are simultaneously and always measured at least while the refrigerant is circulating in the refrigerant circuit.

(Driving restraint control device)
The drive suppression control device 4 is a control device that determines the pressure drop of the refrigerant sucked into the compressor 10 and suppresses the drive of the compressor 10 . Specifically, the actual pressure of the refrigerant immediately before being sucked into the compressor 10 (hereinafter referred to as the actual pressure immediately before suction Pf) does not fall below the allowable lower limit pressure of the compressor 10, which is “0 [MPaG] in gauge pressure”. Control (hereinafter referred to as suppression control) is performed to stop the drive of the compressor 10 or to drive it intermittently so as to prevent the compressor 10 from being overheated. In the drive suppression control device 4, the suppression determination threshold pressure Pb is set to a pressure slightly higher than the allowable lower limit pressure (for example, 0.05 [MPaG] in gauge pressure). The pressure of the refrigerant immediately before being sucked into the compressor 10 is calculated (estimated) from the measured value of the temperature sensor 2 and/or the measured value of the pressure sensor 3, and this calculated (estimated) pressure (hereinafter referred to as pre-suction estimation pressure) becomes smaller than the suppression determination threshold pressure Pb, suppression control is executed.

Then, when the predetermined first condition C1 is satisfied, the drive suppression control device 4 calculates the estimated pressure immediately before intake using the measured value of the temperature sensor 2, and determines the pressure drop of the estimated pressure immediately before intake. to suppress and control the driving of the compressor 10 . On the other hand, when a predetermined second condition C2 different from the first condition C1 is satisfied, the drive suppression control device 4 uses the measured value of the pressure sensor 3 to estimate the pre-intake presumed pressure. Compressor 10 is suppressed and controlled by judging the decrease in pressure.

As shown in FIG. 2(A), the drive suppression control device 4 is realized by an ECU 400 for air conditioners. The ECU 400 includes a CPU (Central Processing Unit) 402, memory 404 such as ROM (Read Only Memory) and RAM (Random Access Memory), and non-volatile storage such as HDD (Hard Disk Drive) and SSD (Solid State Drive). 406 and communication control unit 408 . CPU 402 , memory 404 , storage unit 406 , and communication control unit 408 are communicably connected to each other via internal bus 410 . The communication control unit 408 is connected to the temperature sensor 2, the pressure sensor 3, and (the control driver of) the compressor 10 via a communication line, acquires temperature information and pressure information from the temperature sensor 2 and the pressure sensor 3, and controls the compressor. 10 can transmit a control signal.

A drive suppression control program is stored in the storage unit 406 . The drive suppression control program is read out from the storage unit 406 and developed in the memory 404, and the drive suppression control program developed in the memory 404 is executed by the CPU 402, so that the drive suppression control device 4 shown in FIG. and performs drive suppression control processing.

FIG. 2(B) shows the functional configuration of the drive suppression control device 4 realized by the ECU 400. As shown in FIG. Specifically, the drive suppression control device 4 includes a drive suppression execution processing unit 502 , a pressure detection via temperature estimation processing unit 504 , a pressure detection via pressure estimation processing unit 506 , and a pressure estimation method switching processing unit 508 .

The drive suppression execution processing unit 502 calculates the refrigerant pressure immediately before being sucked into the compressor 10 (hereinafter referred to as immediately before suction estimated pressure) is below the suppression judgment threshold pressure (0.05 [MPaG] in gauge pressure here). Inhibition control such as

The temperature detection-mediated pressure estimation processing unit 504 uses the measured value of the temperature sensor 2 to calculate the estimated pressure immediately before inhalation (hereinafter referred to as the estimated pressure immediately before inhalation via temperature detection). Specifically, the temperature detection via pressure estimation processing unit 504 stores a comparison table (or calculation formula) indicating the temperature-pressure relationship of the refrigerant, and calculates the pressure information from the temperature information. This comparison table (or calculation formula) is preferably based on the saturation curve showing the relationship between the saturation temperature and the saturation pressure of the refrigerant shown in FIG. 3, for example.

The pressure detection-mediated pressure estimation processing unit 506 uses the measured value of the pressure sensor 3 to calculate the estimated pressure immediately before inhalation (hereinafter referred to as the pre-inhalation estimated pressure via pressure detection). In this embodiment, since the pressure sensor 3 measures the pressure of the refrigerant immediately before being sucked into the compressor 10, the measurement result is directly used as the pre-suction estimated pressure via pressure detection. On the other hand, if the location (measuring location) of the pressure sensor 3 is far from just before the refrigerant is drawn into the compressor 10, the pressure Estimated pressure immediately before detection inhalation is calculated.

When pressure is monitored by the drive suppression execution processing unit 502, the pressure estimation method switching processing unit 508 uses the estimated pressure immediately before suction via temperature detection calculated by the pressure estimation processing unit 504 via temperature detection, or performs pressure estimation processing via pressure detection. Switches between using the estimated pre-inhalation pressure via pressure detection calculated in the unit 506 . Specifically, it holds information about conditions for switching determination (here, first condition C1 and second condition C2). A pressure estimation method switching processing unit 508 executes these condition determinations, and switches between refrigerant pressure monitoring using the estimated pressure immediately before suction via temperature detection and refrigerant pressure monitoring using the estimated pressure immediately before suction via pressure detection.

(First condition)
The first condition C1, which is a condition for monitoring the actual pressure Pf immediately before suction of the refrigerant by the measured value of the temperature sensor 2 and estimating (judging) the decrease thereof, is that "the measured value of the temperature sensor 2 is a predetermined monitoring switching criterion. be equal to or lower than the temperature Tr". This monitoring switching reference temperature Tr is preferably set within a range of, for example, -20 [°C] to 10 [°C], and preferably set within a range of -15 [°C] to 5 [°C]. Further, it is preferably set to 0[°C] or less, more preferably -5[°C] or less, and is set to -10[°C] here.

When the first condition C1 is satisfied, the pressure estimation method switching processing unit 508 monitors the pre-inhalation estimated pressure via temperature detection calculated from the measured value of the temperature sensor 2 in the pressure estimation processing unit 504 via temperature detection. A command is sent to the drive suppression execution processing unit 502 . Upon receipt of this command, the drive suppression execution processing unit 502 refers to the estimated pressure immediately before intake via temperature detection over time, and the value of the estimated pressure immediately before intake via temperature detection becomes equal to or less than a predetermined suppression determination threshold pressure Pb. In this case, it is estimated that the actual pressure Pf immediately before suction of the refrigerant has approached the allowable lower limit pressure, and the drive of the compressor 10 is restrained and controlled. Here, the suppression judgment threshold pressure Pb is 0.05 [MPaG] in gauge pressure, but the present invention is not limited to this, and for example, a value in the range of 0.01 [MPaG] in gauge pressure or more and, on the safer side, a value within the range of 0.1 [MPaG] or more and 1 [MPaG] or less is more preferable.

(Second condition)
The second condition C2, which is a condition for monitoring the actual pressure Pf immediately before suction of the refrigerant based on the measured value of the pressure sensor 3 and estimating (determining) the decrease thereof, is that "the measured value of the temperature sensor 2 is equal to the reference temperature Tr It includes "becoming greater than". When the second condition C2 is satisfied, the pressure estimation method switching processing unit 508 monitors the pre-inhalation estimated pressure via pressure detection calculated from the measured value of the pressure sensor 3 in the pressure detection via pressure estimation processing unit 506. A command is sent to the drive suppression execution processing unit 502 . Upon receiving this command, the drive suppression execution processing unit 502 refers to the estimated pressure immediately before inhalation via pressure detection over time, and the value of the estimated pressure immediately before inhalation via pressure detection becomes equal to or less than a predetermined suppression determination threshold pressure Pb. In this case, it is estimated that the actual pressure Pf immediately before suction of the refrigerant has approached the allowable lower limit value, and the drive of the compressor 10 is restrained and controlled.

(Heat pump system control method (control program))
Next, with reference to FIG. 4, a procedure for performing suppression control of the compressor 10 by the drive suppression control device 4 will be described.
First, at least during steady operation in which the refrigerant circulates in the refrigerant circuit 1, the temperature sensor 2 and the pressure sensor 3 measure the temperature of the refrigerant (hereinafter referred to as suction refrigerant temperature) and pressure (hereinafter referred to as suction refrigerant pressure) in step S1. to run. Here, steady operation is a state in which the heat pump system 100 is operated in a non-abnormal state (for example, a state in which refrigerant is leaking from the refrigerant pipe 14, a state in which the refrigerant pipe 14 is blocked, etc.). indicates that

Next, in order to suppress the driving of the compressor 10 in the event of an abnormality, step S2 of monitoring the pressure of the refrigerant is executed. In step S2, first, step S3 is executed to determine whether or not the measured value of the temperature sensor 2 is equal to or lower than the monitoring switching reference temperature Tr.

If the measured value of the temperature sensor 2 is equal to or lower than the monitoring switching reference temperature Tr in step S3, the first condition C1 is assumed to be satisfied (YES), and the estimated pressure immediately before intake via temperature detection is calculated from the measured value of the temperature sensor 2. Step S4a of calculating is executed. On the other hand, when the measured value of the temperature sensor 2 becomes larger than the monitoring switching reference temperature Tr in step S3, the first condition C1 is not satisfied and the second condition C2 is satisfied (NO). Step S4b is executed in which the measured value is used as it is as the estimated pressure immediately before inhalation via pressure detection.

After executing step S4a or step S4b, step S5 is executed to determine whether or not the pre-inhalation estimated pressure is equal to or lower than the suppression determination threshold pressure Pb. If the estimated pressure immediately before suction is equal to or lower than the suppression determination threshold pressure Pb in step S5 (YES), it is estimated that the actual pressure Pf immediately before suction of the refrigerant has approached the allowable lower limit, and the drive of the compressor 10 is suppressed and controlled. S6 is executed. After that, the process returns to step S1. On the other hand, if the estimated pressure immediately before suction is greater than the suppression determination threshold pressure Pb in step S5 (NO), it is estimated that the actual pressure immediately before suction Pf of the refrigerant has moved away from the allowable lower limit value to the safe side, and suppression control is performed. It returns to step S1 without performing.

(Effect)
According to the heat pump system 100 of this embodiment described above, when the first condition C1 is satisfied, the estimated pre-suction pressure is calculated from the measured value of the temperature sensor 2, and when the second condition C2 is satisfied, 2, the measured value of the pressure sensor 3 is estimated as the pre-suction estimated pressure, and the compressor 10 is restrained and controlled when the refrigerant suction pressure becomes lower than the restraint determination threshold pressure Pb.

The first condition C1, ie, the determination that "the measured value of the temperature sensor 2 is equal to or lower than the predetermined monitoring switching reference temperature Tr", tends to deteriorate the monitoring accuracy (pressure estimation accuracy) of the pressure sensor 3. The temperature sensor 2 can ensure sufficient monitoring accuracy (pressure estimation accuracy). In addition, the second condition C2, ``the measured value of the temperature sensor 2 must be greater than the reference temperature Tr,'' can sufficiently ensure the monitoring accuracy (pressure estimation accuracy) of the pressure sensor 3. , the temperature sensor 2 can satisfy a mode in which the monitoring accuracy (pressure estimation accuracy) is likely to deteriorate. In this way, by setting conditions in which each of the temperature sensor 2 and the pressure sensor 3 is good, for example, it is not necessary to use the pressure sensor 3, which can achieve high measurement accuracy under all conditions (measurement range). You get the advantage of That is, the temperature sensor 2 can be used instead of the pressure sensor 3 to monitor the state in which the actual pressure Pf immediately before the refrigerant intake becomes a negative pressure or a pressure close to the atmospheric pressure. As a result, the cost of the pressure sensor 3 can be suppressed by covering the measurement range that the pressure sensor 3 is not good at with the temperature sensor 2, and the state of the sucked refrigerant can be estimated with high accuracy while suppressing the cost of the heat pump system 100 as a whole. and the compressor 10 can be reliably protected.

Also, in this embodiment, the first condition C1 includes that the measured value of the temperature sensor 2 is equal to or lower than the monitoring switching reference temperature Tr (-10[°C]). As shown in FIG. 3, when the refrigerant reaches -10 [° C.], the refrigerant pressure at the time of saturation, that is, just before the suction of the compressor 10 becomes 0.1 [MPaG] in gauge pressure, and the pressure detected by the pressure sensor 3 Approach the pressure region where the measurement accuracy tends to deteriorate. Therefore, when the refrigerant is -10 [° C.] or less, a temperature sensor 2 that can obtain sufficient temperature measurement accuracy is used, and the estimated pressure immediately before suction is calculated from the measured value of the temperature sensor 2 and monitored. 10 can be reliably protected.

By the way, when the refrigerant just before being sucked into the compressor 10 is in a saturated vapor state, it is positioned at a specific point E on the saturated vapor line L in the ph diagram shown in FIG. If the temperature of the refrigerant at this specific point E is measured by the temperature sensor 2, the pressure of the refrigerant can be correctly estimated from the saturation curve of FIG. On the other hand, when the refrigerant immediately before being sucked into the compressor 10 is a superheated gas, the refrigerant is positioned at a specific point E1 in a region having a higher specific enthalpy than the saturated vapor line L shown in FIG.

The isothermal line M1 passing through the specific point E1 of the refrigerant extends curvedly along the vertical axis (pressure axis) in FIG. If the refrigerant is further heated and the degree of superheating of the refrigerant increases immediately before suction while the pressure Px remains the same, the refrigerant shifts to the right, as shown at singular points E2 and E3. As indicated by the isothermal line M2 passing through the singular point E2 and the isothermal line M3 passing through the singular point E3, if the degree of superheating of the refrigerant changes, the temperature of the refrigerant rises even if the pressure Px remains the same. . In other words, when the refrigerant is in a superheated gas state, even if the refrigerant temperature is measured by the temperature sensor 2, only the saturation curve in FIG. 3 (that is, under the assumption that the refrigerant is positioned on the saturated vapor line L in FIG. Then, an error occurs in the pressure estimation. In the operation of the air conditioner, the degree of superheat tends to increase as the temperature of the refrigerant immediately before inhalation increases.

In this regard, in the present embodiment, the second condition C2 includes that the measured value of the temperature sensor 2 is higher than the monitoring switching reference temperature Tr (-10 [°C]). This condition can also be expressed as an operating condition in which the degree of superheat tends to increase. This condition is a state in which sufficient pressure measurement accuracy can be expected even with the pressure sensor 3, and at the same time, it can be said that the temperature sensor 2 is in a state where the pressure estimation accuracy is likely to deteriorate due to an overheated state. As a result, the suctioned refrigerant pressure measured by the pressure sensor 3 can be used for monitoring the compressor 10, and the compressor 10 can be reliably protected.

For the pressure sensor 3, it is desirable that the monitoring switching reference temperature Tr, which is the threshold for separating the first condition C1 and the second condition C2, is higher. For example, assuming that the refrigerant is saturated steam as shown in FIG. 3, the monitoring switching reference temperature Tr can be converted to the monitoring switching reference pressure Pr. Considering the monitoring switching reference pressure Pr, the pressure (gauge pressure) is preferably set within the range of 0.03 [MPaG] to 0.31 [MPaG]. As a result, the temperature sensor 2 can cover a wider range that the pressure sensor 3 is not good at, and the compressor 10 can be protected more reliably.

That is, in the present embodiment, the first condition C1 is that the actual pressure immediately before suction of the refrigerant (including the estimated pressure immediately before suction estimated by some calculation) during steady operation is equal to or lower than the monitoring switching reference pressure Pr. In addition, the second condition C2 may include that the actual pressure immediately before intake during steady operation is higher than the monitoring switching reference pressure Pr. That is, when the actual pressure immediately before suction can be directly measured or estimated without using the temperature sensor 2, the threshold for separating the first condition C1 and the second condition C2 is not the monitoring switching reference temperature Tr. , the monitoring switching reference pressure Pr may be used.

Here, in the present embodiment, the drive suppression control device 4 may further include an overheating suppression execution processing unit 510 as shown in FIG. When the second condition C2 is satisfied, that is, when the degree of superheat is likely to increase, in addition to the suppression control by the drive suppression execution processing unit 502, the overheat suppression execution processing unit 510 outputs the measured value of the temperature sensor 2 and the The compressor 10 may be inhibited and controlled based on the degree of superheat of the refrigerant calculated from the measured value of the pressure sensor 3 . If the degree of superheat becomes abnormally high, for example, there is a possibility that the amount of refrigerant circulating in the path is insufficient. If the operation is continued, the compressor 10 will lock due to insufficient lubrication due to the lean refrigerant. Therefore, by operating the compressor 10 at a low capacity, the circulation amount of the refrigerant is increased to avoid insufficient lubrication and prevent failure of the compressor 10 . In the present embodiment, this control is referred to as "overheat suppression control".

In this case, the overheat suppression execution processing unit 510 of the drive suppression control device 4 stores a table (or calculation formula) indicating the state of the refrigerant, and based on this table (or calculation formula), the temperature sensor 2 measures From both the suctioned refrigerant temperature and the suctioned refrigerant pressure measured by the pressure sensor 3, the degree of superheat ΔT of the refrigerant immediately before being drawn into the compressor is calculated. The superheat suppression execution processing unit 510 monitors the degree of superheat ΔT, and when the degree of superheat ΔT is greater than a predetermined suppression judgment threshold superheat degree ΔTb, it is estimated that, for example, the refrigerant is insufficient. Then, the compressor 10 is stopped, or if the compressor 10 is of a variable displacement type, the compressor 10 is driven with a reduced displacement to ensure lubrication in the compressor 10 . The table (or calculation formula) for calculating the degree of superheat ΔT is based on the ph diagram shown in FIG. 4, for example.

In this embodiment, the temperature sensor 2 and the pressure sensor 3 constantly measure the temperature and pressure of the refrigerant drawn in, so the degree of superheat ΔT of the refrigerant immediately before being drawn into the compressor 10 is always calculated and grasped. You can do it. Therefore, the degree of superheat ΔT can be easily diverted to protect the compressor.

[Modification]
Further, as shown in FIG. 6, in the present embodiment, the heat pump system 100 may further include an environment temperature sensor 30 that measures the temperature of the environment in which the second heat exchanger (heat absorber) 13 is installed. That is, the ambient temperature sensor 30 measures the outside air temperature. In this case, the first condition C1 includes that the measured value of the environmental temperature sensor 30 is equal to or lower than the predetermined monitoring switching reference environmental temperature Ts, and the second condition C2 is that the measured value of the environmental temperature sensor 30 It may include becoming higher than the monitoring switching reference environmental temperature Ts.

In the first condition C1 under which the measured value of the environmental temperature sensor 30 is equal to or lower than the monitoring switching reference environmental temperature Ts (for example, Ts=5 [° C.]), the outside air temperature is low, and the actual intake refrigerant temperature is is low, and as a result, the actual pressure immediately before suction is also low. Therefore, even in a low pressure region, the compressor 10 can be monitored using the temperature sensor 2, which can be expected to have high pressure estimation accuracy, and using the estimated pressure immediately before suction calculated from the measured value of the temperature sensor 2. It is possible to reliably protect the compressor 10 .

On the other hand, under the second condition C2 in which the measured value of the environmental temperature sensor 30 is higher than the monitoring switching reference environmental temperature Ts, the outside air temperature is relatively high, the actual intake refrigerant temperature is high, and the actual pressure immediately before intake is high. is also high. Moreover, immediately before the compressor 10 is sucked, the refrigerant tends to become a superheated gas. Therefore, it is possible to monitor the compressor 10 by estimating the measured value of the pressure sensor 3 as the estimated pressure immediately before suction using the pressure sensor 3, which can be expected to have high measurement accuracy in a high pressure region, and to operate the compressor 10 more reliably. can be protected.

When the measured value of the environmental temperature sensor 30 becomes equal to or lower than the monitoring switching reference environmental temperature Ts, the heating operation mode is selected, and the measured value of the environmental temperature sensor 30 is higher than the monitoring switching reference environmental temperature Ts. The refrigerant circulation path may be switched so that the cooling operation mode (a mode other than the heating operation mode) is selected when the temperature increases.

[Second embodiment]
Next, a heat pump system 200 according to a second embodiment of the invention will be described.
As shown in FIG. 7, the heat pump system 200 according to the present embodiment includes a vehicle heat recovery device 40 that absorbs heat generated in the vehicle by the refrigerant circulating in the refrigerant circuit 1, and switches the refrigerant circulation path in the refrigerant circuit 1. and a possible mode switching controller 41 .

(Heat recovery device)
The vehicle heat recovery device 40 includes a bypass refrigerant pipe 50 that allows refrigerant to be sucked into the compressor 10 without passing through the second heat exchanger (heat absorber) 13, and a third heat exchanger provided in the middle of the bypass refrigerant pipe 50. It has a vessel 51.

The bypass refrigerant pipe 50 is located at a first position P1 on the upstream side of the second heat exchanger (heat absorber) 13 in the refrigerant circuit 1 and a second position between the second heat exchanger (heat absorber) 13 and the accumulator 15. P2 and .

The third heat exchanger 51 causes the refrigerant to absorb heat (exhaust heat) from the internal combustion engine, storage battery, motor, etc., which are the heat sources H of the vehicle, through a heat recovery heat medium (coolant). In the bypass refrigerant pipe 50 , an expansion mechanism 52 is provided between the first position P<b>1 where the bypass refrigerant pipe 50 branches from the refrigerant circuit 1 and the third heat exchanger 51 .

(Mode switching control device)
The mode switching control device 41 is realized by an ECU 400 shown in FIG. 8(A). The hardware configuration of the ECU 400 is the same as that of the first embodiment. As shown in FIG. 8B, as a functional configuration of the ECU 400, in addition to the first embodiment, a mode switching control processing unit 520 is provided. Function. The mode switching control device 41 operates in an outside air heat absorption heating operation mode (corresponding to the heating operation mode in the first embodiment) in which the second heat exchanger (heat absorber) 13 functions as an outdoor unit, and an operation other than the outside air heat absorption heating operation mode. mode, the circulation path of the refrigerant in the refrigerant circuit 1 is switched. In operation modes other than the outside air heat absorption heating operation mode, the refrigerant circulating in the refrigerant circuit 1 is sucked into the compressor 10 via the vehicle heat recovery device 40 without passing through the second heat exchanger (heat absorber) 13. It includes a heat recovery heating mode of operation that allows The operation modes other than the outdoor air heat absorption heating operation mode include the cooling operation mode described in the first embodiment, the defrosting operation mode that melts frost when the outdoor heat exchanger (second heat exchanger 13) is frosted, It also includes a battery heating mode for heating a storage battery by heating a heat recovery heat carrier (coolant).

More specifically, when the mode switching control device 41 switches the operation mode from the outside air heat absorption heating operation mode to the heat recovery heating operation mode, the second heat exchanger (heat absorber) 13 upstream of the refrigerant circuit 1 The first switching valve 55 provided between the expansion mechanism 12 arranged on the side and the first position P1 where the bypass refrigerant pipe 50 branches from the refrigerant pipe 14 is closed, and the bypass refrigerant pipe 50 is provided with By opening the second switching valve 56 , the refrigerant is allowed to flow into the bypass refrigerant pipe 50 , pass through the third heat exchanger 51 , and is led to the compressor 10 . Note that the switching to the heat recovery heating operation mode is performed based on the state of heat generation in the heat source H, the temperature of the heat recovery heat medium (coolant), and the like.

On the other hand, when the mode switching control device 41 switches the operation mode from the heat recovery heating operation mode to the outside air heat absorption heating operation mode, the first switching valve 55 is opened, the second switching valve 56 is closed, and the second switching valve 56 is closed. The refrigerant is led to the compressor 10 through a second heat exchanger (heat absorber) 13 .

(First condition)
In this embodiment, the actual pressure Pf immediately before refrigerant suction is monitored by the measured value of the temperature sensor 2, and the first condition C1, which is the condition for estimating the decrease, is that the mode switching control device 41 switches to the outside air heat absorption heating operation mode. including "switching".

(Second condition)
On the other hand, the second condition C2, which is a condition for monitoring the actual pressure Pf immediately before refrigerant suction based on the measured value of the pressure sensor 3 and estimating the decrease thereof, is that "the mode switching control device 41 is in a mode other than the outside air heat absorption heating operation mode. switching to the operation mode (heat recovery heating operation mode in this embodiment).

(Effect)
According to the heat pump system 200 of the present embodiment described above, the outside air heat absorption heating operation mode is an operation mode that is selected when the outside air temperature is low. is in a low state. Therefore, even in a low pressure region, the compressor 10 can be monitored using the temperature sensor 2, which can be expected to have high pressure estimation accuracy, and using the estimated pressure immediately before suction calculated from the measured value of the temperature sensor 2. Compressor 10 can be reliably protected.

On the other hand, in the heat recovery heating operation mode, the actual intake refrigerant temperature is high and the actual pressure immediately before intake is also high. Therefore, it is possible to monitor the compressor 10 by using the pressure sensor 3, which can be expected to have high measurement accuracy in a high pressure region, and to use the measured value of the pressure sensor 3 as the estimated pressure immediately before suction, thereby protecting the compressor 10 more reliably. can be done.

Therefore, even if the measurement accuracy of the pressure sensor 3 is not high, the compressor 10 can be protected, the cost of the pressure sensor 3 can be suppressed, and as a result, the cost of the heat pump system 200 as a whole can be suppressed. .

In this embodiment, as in the first embodiment, when the second condition C2 is satisfied, that is, when the operation mode is switched to the heat recovery heating operation mode, the intake refrigerant temperature measured by the temperature sensor 2 and the pressure sensor 3 Based on the degree of superheat ΔT of the refrigerant calculated from the suctioned refrigerant pressure measured in (1), the driving of the compressor 10 may be suppressed and controlled during overheating.

Here, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the gist of the present invention.
For example, temperature sensor 2 and pressure sensor 3 do not have to be integrated, and temperature sensor 2 and pressure sensor 3 do not have to measure at the same time. That is, the temperature sensor 2 may be used for measurement only when the first condition C1 is satisfied, and the pressure sensor 3 may be used for measurement only when the second condition C2 is satisfied. Moreover, the temperature sensor 2 and the pressure sensor 3 do not necessarily have to perform measurements all the time, and the temperature sensor 2 and/or the pressure sensor 3 may perform measurements at necessary timings.

The temperature sensor 2 and the pressure sensor 3 measure the discharge refrigerant temperature and the discharge refrigerant pressure on the discharge side (downstream side) of the compressor 10, and from the compression characteristics of the compressor 10, the actual intake refrigerant temperature and the actual pressure may be estimated.

Various first conditions C1 (second conditions C2) described above may be combined as appropriate. For example, when all the first conditions C1 (second conditions C2) described above are satisfied, the temperature sensor 2 ( The driving of the compressor 10 may be controlled based on the measured value of the pressure sensor 3).

According to the heat pump system of the present invention, it is possible to estimate the state of the sucked refrigerant with high accuracy while keeping costs down, and to protect the compressor.

1 Refrigerant circuit 2 Temperature sensor 3 Pressure sensor 4 Drive suppression control device 10 Compressor 11 First heat exchanger 12 Expansion mechanism 13 Second heat exchanger 14 Refrigerant pipe 30 Environmental temperature sensor 40 Vehicle heat recovery device 41 Mode switching control device 100 , 200 heat pump system 400 ECU
Pf Actual pressure immediately before intake Pb Suppression judgment threshold pressure Tr Monitoring switching reference temperature Ts Monitoring switching reference environmental temperature ΔT Superheat degree ΔTb Suppression judgment threshold superheat degree

Claims (8)

A compressor, a radiator, an expansion mechanism, and a heat absorber are connected to each other by refrigerant pipes, and the refrigerant can circulate through the refrigerant pipes in the order of the compressor, the radiator, the expansion mechanism, and the heat absorber. a refrigerant circuit,
a temperature sensor that measures the temperature of the refrigerant;
a pressure sensor that measures the pressure of the refrigerant;
a drive suppression control device that determines a pressure drop of the refrigerant sucked into the compressor and suppresses and controls the compressor so as to suppress the driving of the compressor;
with
The drive suppression control device includes:
when a predetermined first condition is established, the pressure drop of the refrigerant sucked into the compressor is determined from the measurement value of the temperature sensor, and suppression control is performed on the compressor;
When a predetermined second condition different from the first condition is established, the pressure drop of the refrigerant sucked into the compressor is determined from the measurement value of the pressure sensor, and the compressor is suppressed. Heat pump system to control. The first condition includes that the measured value of the temperature sensor is equal to or lower than a predetermined reference temperature,
2. The heat pump system according to claim 1, wherein said second condition includes that the measured value of said temperature sensor is higher than said reference temperature. further comprising an environmental temperature sensor that measures the temperature of the environment in which the heat absorber is installed;
The first condition includes that the measured value of the environmental temperature sensor is equal to or lower than a predetermined reference environmental temperature,
3. The heat pump system according to claim 1, wherein said second condition includes that the measured value of said environmental temperature sensor is higher than said reference environmental temperature. The heat pump system according to any one of claims 1 to 3, which is used as a vehicle air conditioner mounted on a vehicle,
a vehicle heat recovery device that causes the refrigerant circulating in the refrigerant circuit to absorb heat generated in the vehicle;
An outside air heat absorption heating operation mode in which the heat absorber functions as an outdoor heat exchanger that absorbs heat from the outside air into the refrigerant, and an outside air heat absorption heating operation mode in which the refrigerant circulating in the refrigerant circuit is passed through the vehicle heat recovery device without passing through the heat absorber. a mode switching control device capable of switching the circulation path of the refrigerant in the refrigerant circuit between a heat recovery heating operation mode in which the refrigerant is sucked into the compressor by
further comprising
The first condition includes switching the mode switching control device to the outside air endothermic heating operation mode,
The heat pump system, wherein the second condition includes switching the mode switching control device to the heat recovery heating operation mode. The first condition includes that the actual pressure of the refrigerant immediately before being sucked into the compressor during steady operation (hereinafter referred to as the actual pressure immediately before suction) is equal to or lower than a predetermined reference pressure,
5. The heat pump system according to any one of claims 1 to 4, wherein the second condition includes that the actual pressure immediately before suction during steady operation is higher than the reference pressure. The pressure sensor measures the pressure of the refrigerant immediately before being sucked into the compressor,
6. The heat pump system according to claim 5, wherein the drive suppression control device estimates the actual pressure immediately before suction from the measured value of the pressure sensor. The drive suppression control device calculates the degree of superheat of the refrigerant immediately before being sucked into the compressor from the measured value of the temperature sensor and the measured value of the pressure sensor when the second condition is satisfied, The heat pump system according to any one of claims 1 to 6, wherein driving of the compressor is controlled based on the degree of superheat. A heat pump in which a refrigerant circulates through a refrigerant circuit composed of a compressor, a radiator, an expansion mechanism, and a heat absorber, which are connected to each other by refrigerant pipes, in the order of the compressor, the radiator, the expansion mechanism, and the heat absorber. A control method comprising:
a temperature measurement step of measuring the temperature of the refrigerant;
a pressure measuring step of measuring the pressure of the refrigerant;
a drive suppression control step of determining a pressure drop of the refrigerant sucked into the compressor and performing suppression control so as to suppress the driving of the compressor;
including
In the drive suppression control step,
when a predetermined first condition is established, the pressure drop of the refrigerant sucked into the compressor is determined from the measurement value of the temperature sensor, and suppression control is performed on the compressor;
When a predetermined second condition different from the first condition is established, the pressure drop of the refrigerant sucked into the compressor is determined from the measurement value of the pressure sensor, and the compressor is suppressed. A control method for a controlled heat pump system.

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