EXPANSION VALVE DEVICE

Abstract

An expansion valve device includes an electric driver having a stepping motor so as to control an opening degree of a refrigerant passage by displacing a valve member in accordance with a rotation angle of the stepping motor. A controller drives the stepping motor in a micro step when a flow rate of refrigerant flowing through the refrigerant passage is equal to or less than a predetermined value, and drives the stepping motor in a full step when the flow rate of the refrigerant is larger than the predetermined value.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2011-12077 filed on Jan. 24, 2011, the disclosure of which is incorporated herein by reference in its entirety.

FIELD OF THE DISCLOSURE

The present invention relates to an expansion valve device.

BACKGROUND OF THE DISCLOSURE

JP-B2-2898906 describes an electric flow rate control valve (electric expansion valve) used for controlling a flow rate of refrigerant for a refrigerating cycle. The electric flow rate control valve has a valve member that opens or closes a valve port of a fluid passage using a stepping motor. The valve member has a large diameter part and a small diameter part. In a small flow rate region, the flow rate is controlled by controlling only the small diameter part. In a large flow rate region, the flow rate is controlled by controlling the large diameter part. Thus, accuracy for controlling the flow rate in the small flow rate region is raised.

However, the construction is complicated in such two-step valve member having the large diameter part and the small diameter part.

SUMMARY OF THE DISCLOSURE

In view of the foregoing and other problems, it is an object of the present invention to provide an expansion valve device having a simple valve member that can raise the accuracy for controlling the flow rate in the small flow rate region.

According to an example of the present invention, an expansion valve device arranged in a refrigerating cycle so as to decompress and expand refrigerant circulating in the refrigerating cycle includes a housing, a valve member, an electric driver, and a controller. The housing defines a refrigerant passage through which the refrigerant circulates. The valve member is arranged in the housing so as to change an opening degree of the refrigerant passage. The electric driver has a stepping motor, and controls the opening degree of the refrigerant passage by displacing the valve member in accordance with a rotation angle of the stepping motor. The controller drives and controls the stepping motor. The controller drives the stepping motor in a micro step when the opening degree is changed within a first flow rate region where a flow rate of the refrigerant flowing through the refrigerant passage is equal to or less than a predetermined value. The controller drives the stepping motor in a full step when the opening degree is changed within a second flow rate region where the flow rate of the refrigerant flowing through the refrigerant passage is larger than the predetermined value.

Accordingly, the accuracy for controlling the flow rate in the small flow rate region can be raised.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings:

FIG. 1 is a schematic view illustrating an expansion valve device according to an embodiment;

FIG. 2 is a schematic view illustrating a vehicle air-conditioner having the expansion valve device;

FIG. 3 is a graph illustrating a pattern of current supplied to A-phase coil and B-phase coil of a motor of the expansion valve device;

FIG. 4 is a graph illustrating a relationship between a rotor position and a torque curve in the motor;

FIG. 5 is a partially enlarged view of FIG. 4;

FIG. 6 is a graph illustrating a relationship between an actual rotor stop position and an ordered rotor stop position in the motor;

FIG. 7A is a graph illustrating a relationship between a torque curve and a load of the motor when a battery of the vehicle air-conditioner has a voltage of 12V, and

FIG. 7B is a graph illustrating a relationship between a torque curve and a load of the motor when the battery of the vehicle air-conditioner has a voltage of 8V;

FIG. 8A is a graph illustrating a relationship between a torque curve and a load of the motor when a constant current is applied to the motor, and

FIG. 8B is a graph illustrating a relationship between a torque curve and a load of the motor when the constant current is changed from FIG. 8A in accordance with the load; and

FIG. 9 is a graph of a comparison example illustrating a relationship between a torque curve and a load of a motor in which a constant current applied to the motor is not changed irrespective of the load.

DETAILED DESCRIPTION

Embodiments of the present invention will be described hereafter referring to drawings. In the embodiments, a part that corresponds to a matter described in a preceding embodiment may be assigned with the same reference numeral, and redundant explanation for the part may be omitted. When only a part of a configuration is described in an embodiment, another preceding embodiment may be applied to the other parts of the configuration. The parts may be combined even if it is not explicitly described that the parts can be combined. The embodiments may be partially combined even if it is not explicitly described that the embodiments can be combined, provided there is no harm in the combination.

An expansion valve device according to an embodiment is applied to a variable throttle valve 50 shown in FIG. 1. An air-conditioning control device 10 controls the valve 50. FIG. 2 illustrates an air-conditioner apparatus for a vehicle using the valve 50.

As shown in FIG. 2, the air-conditioner apparatus has an air-conditioner unit 1 that performs an air-conditioning for a passenger compartment of the vehicle. Actuators in the unit 1 are controlled by the control device 10 such as ECU. The unit 1 has a refrigerating cycle 3 constructed by a duct 2, a centrifugal type blower, an evaporator 27 and a gas cooler 22. The duct 2 defines an air passage that introduces conditioned-air into the passenger compartment. The blower generates air flow in the duct 2 toward the passenger compartment. The evaporator 27 cools air flowing through the duct 2. The gas cooler 22 reheats the air which passed through the evaporator 27.

The duct 2 is arranged at a front side of the passenger compartment. An inside air inlet 11 and an outside air inlet 12 are defined upstream of the duct 2 in the air flowing direction. The inside air inlet 11 intakes air inside of the passenger compartment (hereinafter referred as inside air). The outside air inlet 12 intakes air outside of the passenger compartment (hereinafter referred as outside air). A switching door 4 is rotatably disposed at inner sides of the inlets 11, 12. The door 4 is driven by an actuator 13 such as a servo motor, and changes the air inlet mode between an outside air introduction mode (FRS) and an inside air circulation mode (REC).

Plural air outlets (not shown) are defined downstream of the duct 2 in the air flowing direction. The outlets includes at least a defroster outlet (DEF), a face outlet (FACE), and a foot outlet (FOOT). The defroster outlet blows off mainly warm air toward an inner surface of a windshield of the vehicle. The face outlet blows off mainly cold air toward an occupant's upper body such as head or breast. The foot outlet blows off mainly warm air toward an occupant's lower body such as foot. The air outlets are selectively opened or closed by plural mode-changing doors (not shown). The mode-changing doors are driven by an actuator 14 such as servo motor, thereby the air outlet mode (MODE) is switched among a face mode (FACE), a bilevel mode (B/L), afoot mode (FOOT), a foot defroster mode (F/D) and a defroster mode (DEF).

The centrifugal type blower has a centrifugal type fan 5 and a blower motor 16 which rotates the fan 5. The fan 5 is rotatbly accommodated in a scroll casing that is integrally formed on the upstream side of the duct 2 in the air flowing direction. A rotation speed of the motor 16 is changed based on a terminal voltage of the blower motor 16 applied through a blower drive circuit (not shown), so that an amount of the air sent into the passenger compartment is controlled.

The refrigerating cycle 3 has a compressor 21, the gas cooler 22, a first decompressor, an outdoor heat exchanger 24, an internal heat exchanger, a second decompressor, the evaporator 27, an accumulator 28, and a refrigerant pipe which connects them annularly.

The compressor 21 is rotated by an internal drive motor (not shown). The compressor 21 is an electric refrigerant compressor which compresses refrigerant drawn from the evaporator 27 to have high temperature and high pressure equal to or higher than a critical pressure, for example, and discharges the refrigerant. The compressor 21 is turned on when electricity is supplied, and is stopped when the electricity supply is stopped. The rotating speed of the compressor 21 is controlled through an inverter 20 so that the compressor 21 has a target rotating speed which is calculated by the ECU 10.

The gas cooler 22 is arranged in the duct 2, downstream of the evaporator 27 in the air flowing direction. The gas cooler 22 is a heat exchanger for heating the passing air through heat exchange with the gas refrigerant which flows from the compressor 21.

Air mix (A/M) doors 6, 7 are rotatably supported by an air-inlet part and an air-outlet part of the gas cooler 22. The door 6, 7 controls a temperature of the air blown into the passenger compartment by controlling an amount of air passing through the gas cooler 22 and an amount of air bypassing the gas cooler 22. The door 6, 7 is driven by an actuator 15 such as servo motor.

The first decompressor is constructed by the variable throttle valve 50 into which the gas refrigerant flows from the gas cooler 22. The variable throttle valve 50 is a first decompression device which decompresses the refrigerant which flows out of the gas cooler 22 based on a valve opening, and may correspond to an electric expansion valve for heating (EVH). The valve opening is electrically controlled by the ECU 10. Moreover, the valve 50 can be set to have a full-open mode by the ECU 10, so that the valve opening of the throttle valve 50 can be fully opened.

The outdoor heat exchanger 24 is disposed at a place which is easy to receive the running wind when the vehicle runs, outside of the duct 2, for example, a front part of an engine compartment of the vehicle. Heat exchange is performed between refrigerant which flows through the inside of the heat exchanger 24 and the outside air sent by an electric fan (not shown). The outdoor heat exchanger 24 operates as a heat sink which absorbs heat from outside air at a heating mode or dehumidification mode, and operates as a radiator which radiates heat to outside air at a cooling mode or dehumidification mode.

The internal heat exchanger is a refrigerant-refrigerant heat exchanger which superheats the refrigerant to be drawn into an inlet port of the compressor 21. Heat exchange is performed between the high-temperature refrigerant flowing out of the outlet of the outdoor heat exchanger 24 and the low-temperature refrigerant flowing out of the outlet of the accumulator 28. The internal heat exchanger has two-layer heat exchange structure in which a face of a low temperature side heat exchanger 29 is tightly in contact with a face of a high temperature side heat exchanger 25 so as to enable the heat exchange.

The second compressor has a variable throttle valve 26 and a bypass pipe 33. Refrigerant flows into the throttle valve 26 from the high temperature side heat exchanger 25 of the internal heat exchanger. Refrigerant flowing out of the high temperature side heat exchanger 25 of the internal heat exchanger is sent to the accumulator 28 by bypassing the throttle valve 26 and the evaporator 27, due to the pipe 33.

The variable throttle valve 26 is a second decompression device which decompresses the refrigerant which flows out of the high temperature side heat exchanger 25 of the internal heat exchanger based on a valve opening. The variable throttle valve 26 is an electric expansion valve for cooling (EVC), and the valve opening is electrically controlled by the ECU 10. An electromagnetic open/close valve 34 (VH) is arranged in the pipe 33. The valve 34 is opened when electricity is supplied, and is closed when the electricity supply is stopped.

The evaporator 27 is an air-refrigerant heat exchanger (heat absorber). The refrigerant decompressed by the throttle valve 26 is evaporated by exchanging heat with air sent by the fan 5. Heat of the air is absorbed by the evaporator 27. The evaporator 27 supplies the gas refrigerant to the low temperature side heat exchanger 29 of the internal heat exchanger and the compressor 21 through the accumulator 28. The accumulator 28 is a gas-liquid separating device which has a storage chamber for storing temporarily the refrigerant flowing from the evaporator 27.

A circulation circuit switching portion of the refrigerating cycle 3 switches the operation mode of the refrigerating cycle 3, that is, the circulation route of refrigerant in the refrigerating cycle 3 is switched among a circulation circuit for the cooling mode (cooling cycle), a circulation circuit for the heating mode (heating cycle), and a circulation circuit for the dehumidification mode or the dehumidification heating mode (dehumidification cycle).

In the present embodiment, the variable throttle valve 50 and the electromagnetic valve 34 may correspond to the circulation circuit switching portion.

Specifically, when the variable throttle valve 50 for heating has the full open mode, and when the electromagnetic valve 34 for heating is closed, the operation mode of the refrigerating cycle 3 is set into the cooling cycle.

Moreover, when the valve 50 has a decompression mode in which the refrigerant is decompressed and expanded to have a small flow rate, and when the valve 34 is opened, the operation mode of the refrigerating cycle 3 is set into the heating cycle.

Moreover, when the valve 50 has the decompression mode, and when the valve 34 is closed, the operation mode of the refrigerating cycle 3 is set into the dehumidification cycle.

Here, the refrigerating cycle 3 of this embodiment uses a refrigerant whose main component is made of carbon dioxide (CO₂) having low critical temperature. The refrigerating cycle 3 is a super critical vapor compression type heat pump cycle. The refrigerant discharged from the outlet port of the compressor 21 has a high pressure equal to or higher than the critical pressure.

In the super critical vapor compression type heat pump cycle, the refrigerant temperature of the inlet part of the gas cooler 22 is raised to about 120° C. by raising the refrigerant pressure on the high pressure side. The refrigerant temperature represents an inlet temperature of refrigerant. That is, the temperature of the refrigerant discharged from the discharge port of the compressor 21 is raised to about 120° C.

In addition, the refrigerant flowing into the gas cooler 22 is not condensed even if the refrigerant radiates heat in the gas cooler 22, because the refrigerant is pressurized by the compressor 21 to have the pressure equal to or higher than the critical pressure.

The ECU 10 includes a known microcomputer having a central processing unit (CPU), a memory (ROM, RAM), an I/O port and a timer function, for example. When an ignition switch of the vehicle is turned on (IG-ON), electricity is supplied to the ECU 10. The ECU 10 electrically controls each actuator (the servo motor 13-15, the blower motor 16, the variable throttle valve 26, 50, the electromagnetic valve 34, and the inverter 20) of the air-conditioning unit 1 based on manipulate signal input from an air-conditioner console panel (not shown), sensor signal input from various sensors, and a control program stored in the memory.

The air-conditioner console panel has a temperature setting switch, an air-conditioner (NC) switch, an air inlet setting switch (FRS/REC switch), an air outlet setting switch (MODE switch), a defroster (DEF) switch, an air amount switch, an auto (AUTO) switch, a turn-off (OFF) switch and the like.

The air-conditioner (NC) switch is a cooling/dehumidification switch that orders cooling/dehumidification for the passenger compartment. The air-conditioner (NC) switch is a setting portion of the cooling/dehumidification that orders the cooling mode or the dehumidification mode among the operation modes of the refrigerating cycle 3. The compressor 21 of the refrigerating cycle 3 may be compulsorily activated by turning on the NC switch, and may be compulsorily stopped by turning off the NC switch.

The DEF switch is a DEF mode fix switch which orders to fix the air outlet mode into the DEF mode. The DEF switch is a fogging prevention switch which removes or prevents the fogging of the windshield.

Further, the DEF switch is a dehumidification mode selecting portion which orders to fix the operation mode of the refrigerating cycle 3 into the dehumidification mode. The dehumidification mode selecting portion sets the dehumidification mode which is one of a dehumidification priority mode or blow-off temperature priority mode.

Alternatively, the dehumidification mode selecting portion may be an anti-fogging sensor that detects the fogging of the windshield, other than the DEF switch. The dehumidification mode selecting portion may be a dehumidification switch that orders only the dehumidification in the passenger compartment without fixing the air outlet mode into the DEF mode when the switch is turned on. The dehumidification mode selecting portion may be a anti-fogging switch that orders only the prevention of the fogging for the windshield without fixing the air outlet mode into the DEF mode when the switch is turned on.

The AUTO switch is a switch which automatically sets the operation mode of the refrigerating cycle 3 into the cooling mode, the heating mode, or the dehumidification mode based on at least a target blow off temperature (TAO). The AUTO switch is an automatic control switch which orders to automatically control each actuator of the air-conditioning unit 1. For example, when the MODE change switch or the air amount setting switch is operated, automatic air-conditioning control for switching the air outlet mode or for controlling the blower motor is cancelled.

A discharge pressure sensor 40 detects a discharge pressure (SP) of the refrigerant discharged from the outlet port of the compressor 21. A discharge temperature sensor 41 detects a discharge temperature (TD) of the refrigerant discharged from the outlet port of the compressor 21. A first refrigerant temperature sensor 42 detects a refrigerant temperature (TCO) discharged from the outlet part of the gas cooler 22. A second refrigerant temperature sensor 43 detects a refrigerant temperature (THO) which flows out of the outlet part of the outdoor heat exchanger 24.

Sensor signals output from the sensors 40, 41, 42 and 43 have ND conversion at an input (ND conversion) circuit (not shown in FIG. 2, refer to an input processor 102 in FIG. 1), and the converted signal is input into the microcomputer.

The discharge pressure sensor 40 is a high pressure detector that detects the high pressure of the refrigerating cycle 3. The discharge temperature sensor 41 is also a refrigerant detector that detects the inlet temperature of the refrigerant which flows into the inlet part of the gas cooler 22.

An outside air temperature sensor 44 detects a temperature of outside air (TAM) which is an air temperature outside of the passenger compartment. A temperature sensor 45 detects an air temperature (TE) just downstream of the evaporator 27, and may correspond to a dehumidification capacity detector. An inside air temperature sensor 46 detects a temperature of inside air (TR) which is an air temperature inside of the passenger compartment. A solar sensor 47 detects a solar radiation amount (TS) into the passenger compartment. A temperature sensor 48 detects an air temperature (TGC) just downstream of the gas cooler 22, and may correspond to a heating capacity detector. Sensor signals output from the sensors 44, 45, 46, 47 and 48 have A/D conversion at the A/D conversion circuit, and the converted signal is input into the microcomputer.

An operation of the air-conditioning apparatus will be described hereinafter.

For example, when the ignition switch is active and when the electricity is supplied to the ECU 10, the ECU 10 selects the operation mode of the refrigerating cycle 3 based on the manipulate signal transmitted from each switch (not shown) of the air-conditioner console panel, the sensor signal transmitted from the various sensors, and the control program stored in the memory. Thus, each actuator (the servo motor 13-15, the blower motor 16, the variable throttle valve 26, 50, the electromagnetic valve 34, and the inverter 20) of the air-conditioning unit 1 is electrically controlled.

For example, when the AUTO switch is turned on so as to perform the automatic air-conditioning control, the ECU 10 intakes the sensor signal from the various sensors, and the manipulate signal from the air-conditioner console panel. The signals are necessary for controlling each air-conditioning member (actuator) in the air-conditioning unit 1.

Next, the target blow off temperature (TAO) of the conditioning air which is blown off into the passenger compartment is computed based on a computing equation beforehand stored in the memory.

Next, the compressor operation judging is performed for determining whether the compressor 21 is turned on or off, based on the air-conditioner (A/C) switch, for example. When a result of the compressor operation judging indicates the turning-on of the compressor 21 based on the previously-computed target blow off temperature (TAO), an operation mode judging is performed for determining the operation mode of the refrigerating cycle 3.

In the operation mode judging, the target blow off temperature (TAO) is compared with a first specified value α (for example, 45° C.) and a second specified value β (for example, 15° C.). In the case of TAO≧α, the heating cycle (heating mode) is chosen as the operation mode of the refrigerating cycle 3. In the case of TAO≦β, the cooling cycle (cooling mode) is chosen as the operation mode of the refrigerating cycle 3. In the case of β<TAO<α, the dehumidification cycle (dehumidification mode) is chosen as the operation mode of the refrigerating cycle 3.

After the operation mode of the refrigerating cycle 3 is chosen, a terminal voltage impressed to the blower motor 16, an opening degree of the door 4 which changes the air inlet mode between the inside air mode and the outside air mode, an opening degree of the mode switching door which change the air outlet mode, and an opening degree of the A/M door 6, 7 are determined, and the actuators are controlled to drive the blower and the doors.

The operation mode of the refrigerating cycle 3 is set. Operational status of the compressor 21 (rotating speed etc.), the opening degree of the variable throttle valve 50, 26, and the opening/closing state of the electromagnetic valve 34 are set and controlled in a manner that the cycle efficiency of the refrigerating cycle 3 is maximized in each operation mode.

When the cooling mode is chosen as the operation mode of the refrigerating cycle 3, the variable throttle valve 50 has the full-open mode, and the electromagnetic valve 34 is closed. The refrigerant discharged from the outlet of the compressor 21 circulates in order of the gas cooler 22, the full-opened valve 50, the outdoor heat exchanger 24, the high temperature side heat exchanger 25, the valve 26, the evaporator 27, the accumulator 28, the low temperature side heat exchanger 29 and the compressor 21, as shown in a blank arrow direction of FIG. 2.

At this time, the opening degree of the A/M door 6, 7 is controlled to have a full-close state (MAX-COOL). The refrigerant of high-temperature and high-pressure discharged from the compressor 21 does not radiate heat while passing through the gas cooler 22. Therefore, the air cooled in the evaporator 27 flows through the duct 2 so as to bypass the gas cooler 22. For example, the air is blown off from the FACE outlet into the passenger compartment, so that the passenger compartment is cooled to have a preset temperature.

In the internal heat exchanger, heat is exchanged between the high temperature and high pressure refrigerant flowing through the high temperature side heat exchanger 25 from the outdoor heat exchanger 24 and the low temperature and low pressure refrigerant flowing through the low temperature side heat exchanger 29 from the accumulator 28. Thus, the high temperature and high pressure refrigerant flowing into the evaporator 27 is cooled. Thereby, the evaporator enthalpy increases, so that the cycle efficiency of the refrigerating cycle 3 can be improved by saving power or electricity.

When the heating mode is chosen as the operation mode of the refrigerating cycle 3, the variable throttle valve 50 has the decompression mode, and the electromagnetic valve 34 is opened. The refrigerant discharged from the outlet of the compressor 21 circulates in order of the gas cooler 22, the valve 50, the outdoor heat exchanger 24, the high temperature side heat exchanger 25, the valve 34, the accumulator 28, the low temperature side heat exchanger 29 and the compressor 21, as shown in a black arrow direction of FIG. 2. At this time, the valve 26 may be fully closed.

At this time, the opening degree of the A/M door 6, 7 is controlled to have a full-open state (MAX-HOT). The high temperature and high pressure refrigerant discharged from the compressor 21 radiates heat to the air in the duct 2 while passing through the gas cooler 22. The air is blown off from the FOOT outlet into the passenger compartment, so that the passenger compartment is heated to have a preset temperature. In the internal heat exchanger, heat exchange is not performed, because low temperature and low pressure refrigerant passes each of the heat exchangers 25, 29.

When the dehumidification mode is chosen as the operation mode of the refrigerating cycle 3, the variable throttle valve 50 has the decompression mode, and the electromagnetic valve 34 is closed. The refrigerant discharged from the outlet of the compressor 21 circulates in order of the gas cooler 22, the valve 50, the outdoor heat exchanger 24, the high temperature side heat exchanger 25, the valve 26, the evaporator 27, the accumulator 28, the low temperature side heat exchanger 29 and the compressor 21, as shown in a hatched arrow direction of FIG. 2.

At this time, air is cooled and dehumidified in the evaporator 27, and the air is reheated in the gas cooler 22. The air is blown off into the passenger compartment from the DEF outlet or the FOOT outlet, for example. The passenger compartment is dehumidified and heated in a manner that the passenger compartment has a preset temperature and in a manner that the fogging of the windshield is removed or prevented.

The discharge pressure of the refrigerant discharged from the compressor 21 and the refrigerant pressure of the outdoor heat exchanger 24 are variable by the throttling degree of the variable throttle valve 50, 26. Thus, the throttling degree is controlled in a manner that the heating capacity of the gas cooler 22 or the dehumidification capacity of the evaporator 27 has a target value. The heating capacity of the gas cooler 22 may be represented by a temperature of air flowing out of the gas cooler or flowing into the passenger compartment. The dehumidification capacity of the evaporator 27 may be represented by a temperature of air flowing out of the evaporator.

Specifically, if the throttling degree is controlled in a manner that the discharge pressure of the refrigerant discharged from the compressor 21 and the refrigerant pressure of the outdoor heat exchanger 24 become low, the outdoor heat exchanger 24 operates as a heat sink, so that the heat amount radiated by the gas cooler 22 increases. At this time, for example, the opening degree of the valve 50 is set as small and the opening degree of the valve 26 is set as large. Therefore, the blow off temperature of the conditioned air blown into the passenger compartment has a comparatively high temperature.

In contrast, if the throttling degree is controlled in a manner that the discharge pressure of the refrigerant discharged from the compressor 21 and the refrigerant pressure of the outdoor heat exchanger 24 become high, the outdoor heat exchanger 24 operates as a radiator, so that the heat amount radiated by the gas cooler 22 decreases. At this time, for example, the opening degree of the valve 50 is set as large and the opening degree of the valve 26 is set as small. Therefore, the blow off temperature of the conditioned air blown into the passenger compartment has a comparatively low temperature.

Next, the variable throttle valve 50 for heating and the air-conditioning control device 10 which controls the valve 50 will be explained.

As shown in FIG. 1, the variable throttle valve 50 is constructed by a housing 51, a seat component 52, a valve 53, a spring 54, a motor 55, a plate component 56, a ring component 57, and an O-ring 58.

The housing 51 is made of metal material, for example, and has an approximately L-shaped refrigerant passage 51a through which the refrigerant circulates. In the housing 51, the cylindrical seat component 52 made of metal material is disposed at the bending part of the refrigerant passage 51a so that inside space of the seat component 52 defines a part of the refrigerant passage 51a. The seat component 52 has a top face, and an inner periphery of the top face defines a seat 52a.

The valve 53 is made of metal material, for example, and is disposed in the refrigerant passage 51a of the housing 51. A main part of the valve 53 has an approximately truncated cone shape, and an outer periphery of a lower end face of the valve 53 defines a seating part which is seated to or separated from the seat 52a of the seat component 52. The valve 53 has a shaft 53a extending upward from the main part in FIG. 2. The shaft 53a is arranged in a through hole part of the housing 51 extending in the axis direction of the shaft 53a, and an upper end of the shaft 53a is located to project from the housing 51.

The motor 55 is constructed by a stepping motor, and is arranged on the upper side of the housing 51. The motor 55 has a case 553 having an approximately dome shape constructed by a cylindrical part and a hemisphere part which closes the upper end of the cylindrical part. A ring-shaped stator 551 is arranged to the outer periphery side of the cylindrical part of the case 553, and a rotor 552 is arranged inside of the cylindrical part.

A lower end of the cylindrical part of the case 553 has a flange part extending outward in the radial direction. The O-ring 58 corresponding to a seal member is interposed between the flange part and the housing 51. The metallic plate component 56 is screwed to the housing 51, and presses the flange part onto the housing 51 through the ring component 57 arranged above the flange part of the case 553. Thereby, the sealing can be achieved between the housing 51 and the case 553 of the motor 55 over all the circumference.

The stator 551 is arranged on the upper side of the plate component 56, and has two-phase structure constructed of an A phase coil 551A and a B phase coil 551B. The motor 55 is, what is called, a two-phase stepping motor.

The rotor 552 arranged in the case 553 is made of magnetic material. The rotor 552 has an approximately pillar-shaped main part 552a and a cylindrical magnet 552b. A part of the main part 552a is removed in ring-recess shape from the both of the upper face and the lower face. The cylindrical magnet 552b is made of a permanent magnet, and is arranged on the outer circumference face of the main part 552a. The cylindrical magnet 552b is magnetized at even pitch in a rotation direction of the rotor 552.

A concave portion is defined in the main part 552a of the rotor 552, and is recessed upward from the center part of the lower face. The upper end of the shaft 53a of the valve 53 is fixed to a ceiling face part of the concave portion.

A female thread is formed on the inner circumference face of the concave portion of the main part 552a of the rotor 552. On the other hand, a cylindrical male thread part 51b is fixed to the housing 51, and projects upward. A male thread is formed on the outer circumference face of the male thread part 51b. The female thread of the main part 552a of the rotor 552 and the male thread of the male thread part 51b are engaged with each other. The rotor 552 is displaced in the axis direction (up-and-down direction in FIG. 1) when the rotor 552 is rotated.

When the rotor 552 is rotated and is displaced in the axis direction, the valve 53 fixed to the main part 552a of the rotor 552 is also displaced, so as to change the opening degree between the valve 53 and the seat 52a.

A construction defined by the motor 55 and the male thread part 51b threaded to the rotor 552 may correspond to an electric driver having a stepping motor and controlling an opening degree of a refrigerant passage by displacing a valve member in accordance with a rotation angle of the stepping motor.

As clearly shown in FIG. 1, the shaft 53a of the valve 53 has a step part. The spring 54 is interposed between the step part and the ceiling face of the main part 552a of the rotor 552. Thereby, if the rotor 552 is displaced downward after the valve 53 is seated on the seat 52a, the spring 54 is compressed, so that excess load is restricted from applying to a seating part defined between the valve 53 and the seat 52a.

Moreover, the rotor 552 is restricted from having excess rotational displacement because a pin component 51c projected from the housing 51 and a pin component 552c projected from the rotor 552 contact with each other.

As shown in FIG. 1, the ECU 10 has an air-conditioning control 101, an input processor 102 and a drive unit 103. The input processor 102 processes a signal input from each switch or sensor, and the processed signal is sent to the air-conditioning control 101. The drive unit 103 outputs a value information determined by the control 101 as an electric signal so as to control each actuator (the servo motor 13-15, the blower motor 16, the throttle valve 26, the electromagnetic valve 34 or the inverter 20).

The ECU 10 further has a step drive control 111, a drive unit 113, and an input processor 112. The step drive control 111 receives a command about a valve opening of the valve 50 that is determined by the air-conditioning control 101, and determines a current value for the motor 50 based on the command. Specifically, a driving direction (rotation direction) of the motor 55 of the valve 50 and a number of steps in the driving of the motor 55 of the valve 50 are set by the step drive control 111, for example.

The drive unit 113 energizes the A-phase coil 551A and the B-phase coil 551B of the stator 551 through PWM control based on the drive information of the valve 50 determined by the step drive control 111. The current values of the A phase coil 551A and the B phase coil 551B are input into the input processor 112, and the input processor 112 performs feedback control relative to the step drive control 111.

The step drive control 111, the input processor 112, and the drive unit 113 may define a controller which drives and controls the stepping motor.

When the cooling mode is selected as the operation mode of the refrigerating cycle 3, the air-conditioner control 101 outputs a valve opening command to the step drive control 111. The valve opening command orders the variable throttle valve 50 to be fully opened.

When the heating mode or dehumidification mode (dehumidification heating mode) is chosen as the operation mode of the refrigerating cycle 3, the air-conditioner control 101 outputs a valve opening command to the step drive control 111. The valve opening command orders the variable throttle valve 50 to decompress and expand the refrigerant in a manner that the operation efficiency of the refrigerating cycle 3 becomes better for performing a desired air-conditioning.

When the step drive control 111 receives the valve opening command from the air-conditioner control 101, the step drive control 111 calculates a driving condition for controlling the position (valve opening) of the valve 53 in the decompression mode where the variable throttle valve 50 decompresses and expands the refrigerant. Further, the step drive control 111 computes a driving condition for performing the mode change between the decompression mode and the full-open mode.

When the step drive control 111 controls the position of the valve 53 in the decompression mode (that is, when the valve 53 is displaced in the low flow rate region where the decompression and expansion is performed), the step drive control 111 calculates a condition for driving the motor 55 in a micro step. That is, the rotation direction (driving direction) of the rotor 552 and the number of micro steps are calculated for displacing the valve 53 to an ordered valve opening position. The number of micro steps represents the number of micro step pulses for the stepping motor 50.

When the step drive control 111 performs the mode change between the maximum flow rate time in the decompression mode and the full-open mode, the step drive control 111 calculates a condition for driving the motor 55 in a full step. That is, the rotation direction of the rotor 552 and the number of full steps (the number of full step pulses) are calculated for displacing the valve 53 to an ordered valve opening position:

A refrigerant flow rate region where the variable throttle valve 50 decompresses and expands the refrigerant may correspond to a first flow rate region in this embodiment. A refrigerant flow rate region where the flow rate is larger than that in the first flow rate region may correspond to a second flow rate region in this embodiment. When the full-open mode is selected, the valve 53 causes the opening degree of the refrigerant passage 51a to have the maximum opening in a manner that the refrigerant flow rate has the maximum value in the second flow rate region.

When the motor 55 is driven in the full step, a gear tooth of the rotor 552 such as magnetic pole of the cylindrical magnet 552b is driven to move by one step from a first position to a second position. The first position is a position opposing to a first gear tooth of the stator 551 such as magnetic pole magnetized by each phase coil. The second position is a position opposing to a second gear tooth of the stator 551 that is adjacent to the first gear tooth of the stator 551.

When the motor 55 is driven in the micro step, a gear tooth of the rotor 552 is driven to move by plural steps from the first position to the second position. That is, in the micro step, a drive angle of the one step in the full step drive is separated into the plural steps, and the motor 55 is stepwise driven by the plural steps. Therefore, it is possible to stop the gear tooth of rotor 552 at a middle position between the first position and the second position.

The step drive control 111 outputs a current command value to the drive unit 113 in a manner that the motor 55 is driven by a constant current correspondingly to the calculated driving direction and the calculated number of pluses. The drive unit 113 supplies electricity to the A phase coil 551A and the B phase coil 551B based on the current command value.

As shown in FIG. 1, a high pressure side refrigerant pressure sensor 40A is arranged for detecting the pressure in the refrigerant passage 51a upstream of the valve 53. The sensor 40A detects the pressure of refrigerant before decompressed by the throttle valve 50 in the refrigerating cycle. The sensor 40A is omitted in the explanation of the refrigerating cycle using FIG. 2.

The step drive control 111 changes the value of the constant current driving the motor 55 in accordance with the refrigerant pressure detected by the sensor 40A. Specifically, the value of the constant current is increased as the detected refrigerant pressure becomes high.

The sensor 40A is not limited to be placed in the refrigerant pipe directly upstream of the throttle valve 50. For example, the sensor 40A may be arranged in the housing 51 so as to face the refrigerant passage 51a upstream of the valve 53. A high pressure side pressure detector may correspond to the sensor 40A, or a combination of the sensor 40A and the discharge pressure sensor 40.

Although detailed explanation was omitted, the throttle valve 26 for cooling may have the same construction as the throttle valve 50 for heating. Therefore, the variable throttle valve 26 for cooling and the variable throttle valve 50 for heating can be made common.

According to the embodiment, the step drive control 111 selectively switches the decompression mode and the full-open mode, based on the valve opening command output from the A/C control 101. The decompression mode is selected when the throttle valve 50 is required to decompress the refrigerant which circulates in the refrigerant passage 51a, so that the refrigerant is decompressed and expanded in the low flow rate region. The full-open mode is selected when the throttle valve 50 is not required to decompress and expand the refrigerant which circulates in the refrigerant passage 51a, so that the valve 53 is positioned at the maximum opening position so as to have the maximum refrigerant flow rate.

In the decompression mode, the valve 53 is displaced by driving the motor 55 corresponding to the stepping motor in the micro step, and the flow rate control is performed for refrigerant.

When the mode change is performed between the decompression mode and the full-open mode, the valve 53 is displaced by driving the motor 55 in the full step.

Therefore, accuracy for controlling the refrigerant flow rate can be improved at the decompression mode. Further, the mode change can be quickly performed between the decompression mode and the full-open mode.

Moreover, when the step drive control 111 drives the motor 55 through the drive unit 113, the step drive control 111 computes the driving direction and the number of pulses, and the motor 55 is driven by the constant current in accordance with the drive pulse. Thereby, the motor 55 constructed by the stepping motor can be driven stably.

When the mode change is performed between the decompression mode and the full-open mode, the motor 55 is driven by the constant current, similarly to the decompression mode. At least, when the valve opening is changed in the low flow rate region at the decompression mode, it is desirable to drive the motor 55 in the micro step by using the constant current. Thereby, even when a voltage supplied from a power source is varied, the motor 55 can be stably driven in the micro step due to the constant current.

Referring to FIGS. 3-7B, the reasons of the above advantages will be described hereinafter. FIG. 3 shows a graph which illustrates a current input into the A phase coil and a current input into the B phase coil when the motor is driven in the micro step having sixteen separated steps. FIG. 4 shows a graph illustrating a torque curve that represents a relationship between the rotor angle (rotor position) and the torque when the current pattern of FIG. 3 is used. FIG. 5 shows an enlarged part of the torque curve of FIG. 4.

As shown in FIG. 3, relative to an angle of the one step in the full step drive, the current supplied to the A phase coil is stepwise increased in the separated sixteen steps, and the current supplied to the B phase coil is stepwise decreased in the separated sixteen steps. A force attracting the rotor 552 between the phases is gradually changed step by step. It becomes possible to stop the rotor 552 at a point at which the attracting force is balanced each time, so that the micro step drive can be performed by dividing the angle in the full step drive into the sixteen steps.

However, as shown in FIG. 4, the torque curve tends to have variation in a mountain portion or a valley portion at which an absolute value of the torque is large. Further, a variation amount also becomes small in the mountain portion and the valley portion because a gradient of the torque curve becomes small.

Therefore, as shown in FIG. 5, a resolution of the rotor stop position is lowered in a high-load case where the load of the motor 55 is high because the mountain portion or the valley portion is coincident with the high-load case, compared with a low-load case. The high-load case and the low-load case are just examples showing a high-low relationship, and have no relationship with the load level of the throttle valve 50.

FIG. 6 shows an actual (real) stop position of the rotor relative to an ordered stop position of the rotor when the drive load having the level shown in FIG. 5 is added. The actual stop position is separated largely from an ideal value in the case of high-load because the mountain portion of the torque curve is used, compared with the case of low-load.

In a case where the motor 55 is driven by applying voltage in place of the constant current, if the voltage falls, the motor torque also falls. Therefore, the resolution is further lowered in the high-load case. The air-conditioner apparatus of the present embodiment is for the vehicle. If a battery mounted on the vehicle is lowered, the lowering in the resolution becomes remarkable in the case where the motor is driven by applying the voltage.

For example, FIG. 7A shows a case where the battery has a voltage of 12V, and FIG. 7B shows a case where the battery has a voltage of 8V. In FIG. 7A, the load level is separated far from the mountain portion (peak part) of the torque curve. However, if the voltage of the battery falls to 8V, as shown in FIG. 7B, the load level becomes close to the mountain portion of the torque curve, so that the resolution may get worse extremely.

According to the present embodiment, the motor 55 is driven by the constant current. Therefore, the torque generated by the motor becomes approximately constant irrespective of the voltage of the power source. For example, even if the voltage of the battery falls from 12V to 8V, the state shown in FIG. 7A can be maintained.

FIGS. 7A and 7B show a schematic torque curve when the motor is driven in the micro step having four steps, for easy understanding, differently from FIGS. 4-6. The same thing is applied to FIGS. 8A-9 which are used for the subsequent explanation.

According to the embodiment, the step drive control 111 increases the constant current, as the refrigerant pressure detected by the high-pressure side refrigerant pressure sensor 40A becomes large. If the refrigerant pressure is increased on the upstream side of the valve 53 in the refrigerant passage 51a, a refrigerant pressure difference between the upstream side and the downstream side of the valve 53 in the refrigerant passage 51a increases, so that the level of the drive load is raised.

Therefore, when the motor 55 is driven in the micro step using the constant current, if the current value is increased based on an increase in the refrigerant pressure upstream of the valve 53 in the refrigerant passage 51a, the torque generated by the stepping motor can be increased correspondingly to the increased drive load. Thus, even if the drive load becomes large, the motor 55 can be stably driven in the micro step.

In other words, by estimating the load level based on the refrigerant pressure value upstream of the valve 53, and by changing the constant current value based on the estimated load level, the resolution can be maintained as high.

FIG. 9 illustrates a comparison example relative to the embodiment, in which the load level is increased from A level to B level. If the constant current value is not changed, the torque is not changed from the maximum value of X. In this case, a ratio of the load level to the maximum torque X is lowered greatly.

That is, a difference between a value of A/X and a value of B/X becomes large, so that the resolution will be lowered greatly.

In contrast, according to the embodiment, the current value of the constant current drive is increased in accordance with an increase in the refrigerant pressure upstream of the valve 53 in the refrigerant passage 51a. Therefore, as shown in FIGS. 8A and 8B, if the load level is increased from A level of FIGS. 8A to B level of FIG. 8B, the value of the constant current is increased, so the torque can be increased from “X1” in FIG. 8A to “X2” in FIG. 8B. Thereby, the ratio of the load level to the maximum torque can be restricted from decreasing. That is, the difference between A/X1 and B/X2 can be made small, so that the resolution can be restricted from having large decreasing, although a slight decreasing may be generated.

The present invention is not limited to the above embodiment.

The number of the micro steps is not limited to sixteen, and can be arbitrarily set.

The step drive control 111 may increase the current value of the constant current drive based on an increase in a pressure difference between the upstream side and the downstream side of the valve 53, in place of the increase in the refrigerant pressure upstream of the valve 53 in the refrigerant passage 51a. Alternatively, the constant current value may be controlled based on sensor information transmitted from three or more sensors.

The motor 55 may be a plural-phase stepping motor other than the two-phase stepping motor. For example, The motor 55 may be a five-phase stepping motor.

The motor 55 is not limited to be driven by the constant current. The motor 55 may be driven by applying a voltage if a predetermined resolution can be secured.

In the embodiment, the motor 55 is driven in the micro step in the first flow rate region at the decompression mode, and is driven in the full step in the second flow rate region when the mode change is performed between the decompression mode and the full-open mode.

In other words, the controller can selectively switch the decompression mode and the full-open mode. When it is necessary to decompress the refrigerant which circulates in the refrigerant passage 51a, the refrigerant is decompressed and expanded in the first flow rate region at the decompression mode. When it is not necessary to decompress the refrigerant, the valve 53 causes the opening degree of the refrigerant passage 51a to have the maximum opening so that the refrigerant has the maximum flow rate in the second flow rate region at the full-open mode.

When the valve opening is changed within the first flow rate region, the motor 55 is driven in the micro step. When the operation mode is switched between the decompression mode and the full-open mode, the motor 55 is driven in the full step. That is, in the second flow rate region, the flow rate control is performed only at the maximum flow rate.

However, the present invention is not limited to the above control. For example, the flow rate control may be performed in the whole of the second flow rate region. That is, the motor 55 may be driven in the micro step when the controller controls the valve opening in the first flow rate region in which the flow rate of refrigerant circulating in the refrigerant passage 51a is equal to or lower than a predetermined value. Further, the motor 55 may be driven in the full step when the controller controls the valve opening in the second flow rate region in which the flow rate of refrigerant circulating in the refrigerant passage 51a is higher than the predetermined value.

The refrigerating cycle 3 may be a vapor compression heat pump cycle in which the high pressure side pressure is equal to or lower than the critical pressure, other than the supercritical vapor compression heat pump cycle.

The present invention may be applied to a stationary type refrigerating cycle other than the refrigerating cycle for the vehicle air-conditioner.

Such changes and modifications are to be understood as being within the scope of the present invention as defined by the appended claims.

Claims

1. An expansion valve device arranged in a refrigerating cycle, the expansion valve device decompressing and expanding refrigerant circulating in the refrigerating cycle, the expansion valve device comprising:

a housing defining a refrigerant passage through which the refrigerant circulates;

a valve member arranged in the housing so as to change an opening degree of the refrigerant passage;

an electric driver having a stepping motor so as to control the opening degree of the refrigerant passage by displacing the valve member in accordance with a rotation angle of the stepping motor; and

a controller that drives and controls the stepping motor, wherein

the controller drives the stepping motor in a micro step when the opening degree is changed within a first flow rate region where a flow rate of the refrigerant flowing through the refrigerant passage is equal to or less than a predetermined value, and

the controller drives the stepping motor in a full step when the opening degree is changed within a second flow rate region where the flow rate of the refrigerant flowing through the refrigerant passage is larger than the predetermined value.

2. The expansion valve device according to claim 1, wherein

the controller selectively switches an operation mode of the refrigerating cycle between a decompression mode and a full-open mode,

in the decompression mode, the refrigerant is decompressed and expanded within the first flow rate region when it is necessary to decompress the refrigerant passing through the refrigerant passage,

in the full-open mode, the valve member causes the opening degree of the refrigerant passage to become the maximum in a manner that the flow rate of the refrigerant flowing through the refrigerant passage becomes the maximum within the second flow rate region when it is unnecessary to decompress the refrigerant passing through the refrigerant passage, and

the controller drives the stepping motor in the full step when the controller switches one of the decompression mode and the full open mode into the other.

3. The expansion valve device according to claim 1, wherein

the controller drives the stepping motor in the micro step by supplying a constant current when the opening degree is changed in the first flow rate region.

4. The expansion valve device according to claim 3, wherein

the controller increases the constant current in accordance with an increase in a pressure difference between a pressure of the refrigerant upstream of the valve member and a pressure of the refrigerant downstream of the valve member, or the controller increases the constant current in accordance with an increase in a pressure of the refrigerant upstream of the valve member.