JP2003322435A - Expansion valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain a refrigerant flow rate, and to reduce a refrigerant flowing sound by delaying a pressure fluctuation in a pressure chamber in a power element on the basis of a pressure drop in a low pressure refrigerant passage of an expansion valve at compressor starting time in a refrigerating cycle. <P>SOLUTION: A collar member 40 is pressed in a temperature sensing bar 36f for penetrating through an expansion valve body 30. The collar member 40 is integrally formed of a large diameter disk part 40a, and a small diameter cylinder part 40b rising from one surface, and has a through hole 40c in the center. The temperature sensing bar 36f is inserted into the through hole 40c. The disk part 40a is inserted into a lower pressure chamber 36c by abutting to a step part 30a of the valve body 30 formed between a lower pressure chamber 36c and a pressure equalizing hole 36e, and the cylinder part 40b is inserted into the pressure equalizing hole 36e. A small hole 30b for communicating the lower pressure chamber 36c with the low pressure refrigerant passage 34 is formed in parallel to the temperature sensing bar 36f in the step part 30a of the valve body 30. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an expansion valve used for controlling a flow rate of a refrigerant supplied to an evaporator in a refrigerating cycle such as an air conditioner or a refrigerating device.

[0002]

2. Description of the Related Art An expansion valve of this type is used in a refrigeration cycle of an air conditioner such as an automobile.
The longitudinal cross-sectional view of an example of the expansion valve widely used conventionally is shown with the outline of the refrigeration cycle. In the figure, an expansion valve 10 is provided in a prism-shaped aluminum valve body 30 at a portion of a refrigerant line 11 of a refrigeration cycle that extends from a refrigerant outlet of a condenser 5 to a refrigerant inlet of an evaporator 8 via a receiver 6. The first passage 32 serving as a high-pressure side passage through which the high-pressure liquid-phase refrigerant passes and the third passage 32 ′ serving as a low-pressure side passage through which the adiabatic gas-liquid two-phase refrigerant that has been adiabatically expanded flows.
And a second passage 34, which is a low-pressure refrigerant passage interposed in a portion of the refrigerant pipe 11 extending from the refrigerant outlet of the evaporator 8 to the refrigerant inlet of the compressor 4, are separated from each other vertically by a partition wall 38f, and the valve main body is separated. It is formed inside 30.

An orifice 32a for adiabatically expanding the liquid refrigerant supplied from the refrigerant outlet of the receiver 6 is formed between the first passage 32 and the third passage 32 '. A valve seat is formed on the inlet side of the orifice 32a, that is, on the upstream side of the first passage, and a spherical valve body 32b supported by a valve member 32c from the upstream side is arranged on the valve seat, and a valve body 32b is provided. It is fixed to the valve member 32c by welding. The valve member 32c is arranged between the valve body and an urging means 32d such as a compression coil spring provided in the lower portion of the valve body, and transmits the urging force of the urging means 32d to the valve body 32b. It is biased toward the seat.

First, the liquid refrigerant from the receiver 6 is introduced
32 becomes a passage for liquid refrigerant, and the inlet port 321
And a valve chamber 35 continuous with the inlet port 321. The valve chamber 35 is a bottomed chamber formed coaxially with the orifice 32a, and is closed by a plug 39,
The first passage 32 communicates with the third passage 32 ′ via the orifice 32 a, and is connected from the outlet port 322 to the refrigerant inlet of the evaporator 8 by the refrigerant pipe 11.

Further, in order to open and close the orifice 32a by giving a driving force to the valve body 32b in the valve body 30 according to the outlet temperature of the evaporator 8, a small diameter hole 37 and a diameter larger than this hole 37 are provided. A hole 38 having a diameter is formed so as to penetrate the second passage 34 and coaxially with the orifice 32a, and the power element portion 3 serving as a temperature-sensitive driving portion is provided at an upper end outside the valve body 30.
6 is formed with a screw hole 361 for fixing 6 through a sealing material 36m.

The power element section 36 is a diaphragm 36a made of stainless steel, which is a flexible thin metal plate.
And the diaphragm 36a is sandwiched between them by welding, and the diaphragm is used as one wall surface.
An upper cover 36d made of stainless steel and serving as an airtight wall which constitutes an upper pressure chamber 36b which is a first pressure chamber and two lower pressure chambers 6c which are two pressure chambers which are divided into upper and lower portions. And a lower cover 36h, a blind plug 36i for enclosing a predetermined refrigerant serving as a diaphragm driving medium in the upper pressure chamber 36b, and the lower pressure chamber 36c.
Are communicated with the second passage 34 via a pressure equalizing hole 36e formed concentrically with respect to the center line of the orifice 32a. The refrigerant vapor from the evaporator 8 flows through the second passage 34, the passage 34 becomes a passage for the vapor-phase refrigerant, and the pressure of the vapor-phase refrigerant is reduced through the pressure equalizing hole 36e to the lower pressure chamber 36c.
Is loaded on. In addition, a cylindrical mounting seat 362 is formed on the lower cover 36h, and the mounting seat 362 has a screw hole 361.
It is attached to the valve body 30 by screwing and is fixed to the valve body 30.

Further, the refrigerant of the evaporator 8 is disposed in the lower pressure chamber 36c so as to be in contact with the diaphragm 36a and penetrate the second passage 34 to be slidable in the large-diameter hole 38 in the partition wall 38f. It is made of aluminum that transmits the outlet temperature to the lower pressure chamber 36c and slides in the large-diameter hole 38 according to the displacement of the diaphragm 36a due to the pressure difference between the upper pressure chamber 36b and the lower pressure chamber 36c to give a driving force. The thickened temperature sensitive rod 36f and the small-diameter hole 37 are slidably arranged in the hole 37 and bias the valve element 32b in accordance with the displacement of the temperature sensitive rod 36f.
The operating rod 37f is made of stainless steel and has a smaller diameter than the temperature sensitive rod 36f that presses against the elastic force of d. The temperature sensitive rod 36f is provided with airtightness between the first passage 32 and the second passage 34. A sealing member for securing, for example, an O-ring 36g is provided. The upper end portion 36k of the temperature sensitive rod 36f has the diaphragm 3
It has a stopper portion 36L which is in contact with the lower surface of 6a and serves as a receiving portion and which is enlarged in the radial direction in order to obtain a contact area with the diaphragm. The displacement of the diaphragm 36a is transmitted to the valve body 32b via the temperature sensitive rod 36f, and
The stopper portion 36L is supported by the lower cover 36h so that the upper end portion 36k of f slides in the lower pressure chamber 36c.

Further, the lower end of the temperature sensitive rod 36f abuts the upper end of the operating rod 37f at the bottom of the large diameter hole 38, and the operating rod 3f
The lower end of 7f is in contact with the valve body 32b, and the temperature sensing rod 36f
The operating rod 37f constitutes a temperature-sensitive drive rod, and this temperature-sensitive drive rod serves as a transmission member for transmitting the displacement of the diaphragm 36a to the valve element 32b.

The power element portion 36 and the temperature sensitive rod 3 described above.
6 and the operating rod 37f, the operating rod 37f is inserted into the small-diameter hole 37, and the temperature sensitive rod 36f is inserted into the large-diameter hole 38.
After being inserted into the inside, the mounting seat 362 of the lower cover 36h is fixed by being screwed into the screw hole 361,
The ring 36m ensures airtightness between the lower cover 36h and the valve body 30, and the screw hole 361 constitutes the lower pressure chamber 36c together with the lower cover 36h and the diaphragm 36a.

Therefore, in the pressure equalizing hole 36e, the orifice 32 of the first passage 32 is formed from the lower surface of the diaphragm 36a.
The valve body drive rod extending to a is arranged concentrically. The portion 37e of the operating rod 37f is formed thinner than the inner diameter of the orifice 32a.
The refrigerant passes through the inside of the orifice 32a.

In the above structure, the upper pressure chamber 36b of the power element section 36 is filled with a predetermined refrigerant as a diaphragm driving medium (for example, the same as the refrigerant gas used in the refrigeration cycle), and the diaphragm driving medium is filled with the refrigerant. Is from the refrigerant outlet of the evaporator 8 flowing through the second passage 34 through the temperature sensing rod 36f and the diaphragm 36a exposed to the second passage 34 and the pressure equalizing hole 36e communicating with the second passage 34. The pressure and temperature of the refrigerant are transmitted.

The diaphragm driving medium in the upper pressure chamber 36b is gasified and the pressure thereof changes according to the transmitted temperature, and the medium is loaded on the upper surface of the diaphragm 36a. The diaphragm 36a is displaced vertically due to the difference between the pressure of the diaphragm driving gas loaded on the upper surface and the pressure loaded on the lower surface of the diaphragm 36a. The vertical displacement of the center of the diaphragm 36a is transmitted to the valve body 32b via the temperature-sensitive drive rod to move the valve body 32b toward or away from the valve seat of the orifice 32a. As a result, the refrigerant flow rate is controlled.

That is, the temperature sensitive rod 36f is arranged in the second passage 34 connected to the outlet side of the evaporator 8, and the temperature of the low-pressure gas-phase refrigerant sent from the evaporator is transmitted to the upper pressure chamber 36b. Therefore, since the pressure of the upper pressure chamber 36b changes according to the temperature of the pressure and the outlet temperature of the evaporator 8 is high, that is, when the heat load of the evaporator increases, the pressure of the upper pressure chamber 36b increases and accordingly Since the temperature sensitive rod 36f, that is, the temperature sensitive drive rod is driven downward to lower the valve body 32b, the opening degree of the orifice 32a becomes large. As a result, the amount of refrigerant supplied to the evaporator 8 is increased, and the temperature of the evaporator 8 is lowered. On the contrary, the temperature of the refrigerant sent from the evaporator 8 decreases. That is, when the heat load on the evaporator is reduced, the valve body 32b is driven in the opposite direction to the above, the opening degree of the orifice 32a is reduced, the supply amount of the refrigerant to the evaporator is reduced, and the temperature of the evaporator 8 is increased. .

[0014]

By the way, in the above-mentioned conventional expansion valve, when the compressor 4 is started, the pressure in the low-pressure refrigerant passage 34 suddenly drops, and the first pressure chamber and the second pressure in the power element portion 36 are reduced. The pressure difference between the chamber and the chamber becomes large, and the displacement of the diaphragm 36k due to this causes the temperature sensitive rod 36f and the operating rod 37f to be driven downward and the valve body 32b.
Therefore, the valve body 32b is separated from the orifice 32a, the orifice 32a is fully opened, and the flow rate of the refrigerant from the receiver 6 to the evaporator 8 through the first passage 32 that is the high-pressure passage is close to the maximum. It becomes a state. Therefore, the flow noise of the refrigerant generated when the refrigerant passes through the orifice 32a is large, and particularly in the case of the gas-liquid two-phase refrigerant, there is a problem that the flow noise of the refrigerant becomes large.

The present invention has been made in view of the above circumstances, and an object thereof is to delay the pressure drop of the low pressure refrigerant passage of the expansion valve at the time of starting the compressor, thereby avoiding the fully opened state of the orifice and allowing the refrigerant flow. An object is to provide an expansion valve capable of reducing noise.

[0016]

Therefore, an expansion valve according to a first aspect of the present invention is a high-pressure side passage, a low-pressure side passage, an orifice communicating between these passages, a low-pressure refrigerant passage, and a valve element arranged to face the orifice. A valve body having a valve body inside thereof, a power element provided outside the valve body having a pressure chamber partitioned by a diaphragm, and a displacement of the diaphragm according to a pressure fluctuation of the pressure chamber to drive the valve body. In the temperature-sensitive drive rod and the expansion valve in which the opening degree of the orifice is controlled by the valve body, a delay means for delaying the pressure fluctuation in the pressure chamber due to the pressure drop in the low pressure refrigerant passage is provided inside the valve body. It is characterized by doing. With this expansion valve, it is possible to delay the pressure fluctuation of the pressure chamber of the power element due to the pressure drop of the low pressure refrigerant passage at the time of compressor startup, suppress the flow rate of the refrigerant passing through the orifice, and reduce the refrigerant flow. You can reduce the sound.

An expansion valve according to a second aspect is the expansion valve according to the first aspect, wherein the delay means is a blocking member that is provided between the low-pressure refrigerant passage and the pressure chamber to block the pressure transmission. It is characterized by being a small hole for transmitting the pressure drop to the pressure chamber. As a result, the pressure drop in the low-pressure refrigerant passage is transmitted to the pressure chamber via the small hole, so that the pressure drop can be transmitted slowly.

An expansion valve according to a third aspect is the expansion valve according to the second aspect, wherein the delay means is a collar member and a bleed port. With such a configuration, the refrigerant flow noise can be reduced without significantly changing the configuration of the conventional expansion valve.

An expansion valve according to a fourth aspect is a valve having therein a high-pressure side passage, a low-pressure side passage, an orifice communicating between these passages, a low-pressure refrigerant passage and a valve body arranged to face the orifice. Displacement of a diaphragm that defines a main body, a power element provided outside the valve main body, and a second pressure chamber that communicates the power element with a first pressure chamber containing a predetermined refrigerant and the low-pressure refrigerant passage. In the expansion valve including the temperature-sensitive drive rod that drives the valve body, the temperature-sensitive drive rod is equipped with a blocking unit that blocks communication between the second pressure chamber and the low-pressure refrigerant passage, The valve body is characterized in that a small hole that communicates the second pressure chamber and the low-pressure refrigerant passage is formed. With this expansion valve, the pressure drop in the low-pressure refrigerant passage can be delayed and transmitted to the second pressure chamber through the small hole.
Since the pressure fluctuation due to the pressure drop in the low-pressure refrigerant passage of the first pressure chamber is delayed and generated, the flow rate of the refrigerant passing through the orifice can be suppressed and the refrigerant flow noise can be reduced.

In the expansion valve of the fifth aspect, the high pressure side passage and the low pressure side passage through which the refrigerant flows toward the evaporator, the orifice communicating between these passages, the low pressure refrigerant passage through which the refrigerant sent from the evaporator passes, and the orifice. Depending on the pressure and temperature of the refrigerant sent out from the evaporator by the valve body having the valve body arranged oppositely, the power element provided outside the valve body, and the predetermined refrigerant enclosed in the power element. The first pressure chamber whose internal pressure changes and the second pressure chamber communicating with the low-pressure refrigerant passage, the temperature-sensitive drive rod driven by the displacement of the diaphragm, and the valve body. And a spring for biasing the orifice side, and the valve body is brought into contact with and separated from the orifice by the temperature-sensitive operating rod. In the expansion valve for controlling the flow rate of the refrigerant toward the, the avoidance means for avoiding the fully opened state of the orifice at a pressure drop of the low-pressure refrigerant passage, characterized by comprising within the valve body. According to such an expansion valve, it is possible to avoid the fully opened state of the orifice due to the rapid change in the differential pressure between the first pressure chamber and the second pressure chamber due to the pressure drop in the low pressure refrigerant passage at the time of starting the compressor, and to pass through the orifice. The flow rate of the refrigerant can be suppressed and the refrigerant flowing noise can be reduced.

An expansion valve according to a sixth aspect is the expansion valve according to the fifth aspect, wherein the avoidance means includes the low pressure refrigerant passage and the second
The blocking means is provided between the pressure chambers and blocks the communication between the pressure chambers, and reduces the pressure drop in the low pressure refrigerant passage.
It is characterized in that it is a small hole provided in the valve body for transmitting to the pressure chamber. According to such an expansion valve, the pressure drop in the low-pressure refrigerant passage is slowly transmitted to the second pressure chamber through the small hole, so that a rapid change in the differential pressure between the first pressure chamber and the second pressure chamber can be suppressed. It is possible to avoid the fully opened state of the orifice based on the differential pressure, suppress the flow rate of the refrigerant passing through the orifice, and reduce the refrigerant flow noise.

An expansion valve according to a seventh aspect is the expansion valve according to the sixth aspect, wherein the blocking means is a collar member provided on the temperature-sensitive drive rod, and the small hole is substantially parallel to the temperature-sensitive drive rod. It is a bleed port provided in the. According to such an expansion valve, the refrigerant flow noise can be reduced without significantly changing the configuration of the conventional expansion valve.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of an expansion valve according to the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing an embodiment of an expansion valve, and a refrigeration cycle is omitted. In FIG. 1, the basic configuration is the same as the conventional expansion valve shown in FIG. 2, and the same reference numerals as those in FIG.
In the expansion valve 10 ′, the same or equivalent parts are shown, and the valve body 3
No. 0 uses the same valve body as that of the conventional example shown in FIG. 2, and is basically formed between the high pressure side flow passage 32 and the low pressure side flow passage 32 ′ through which the high pressure refrigerant sent to the evaporator passes. An orifice 32a, a spherical valve body 32b arranged so as to face the orifice 32a from the upstream side of the refrigerant, and a biasing means 32d for biasing the valve body from the upstream side toward the orifice. A low pressure refrigerant sent from an evaporator through which a low pressure refrigerant passage 34 passes, and a valve member 32c arranged between the urging means and the valve body to transmit the urging force of the urging means to the valve body 32b. Power element section 36 that operates in response to pressure temperature
And a temperature-sensitive drive rod that is inserted between the valve 32b and a temperature-sensitive rod 36f and an operating rod 37f that are inserted between the valve body 32b and the temperature-sensitive drive rod. Since the valve body 32b is brought into contact with and separated from the orifice 32a by a rod,
The flow rate of the refrigerant passing through the orifice 32a is controlled.

The temperature sensitive drive rod has a power element portion 36 at its upper end portion 36k and an upper pressure chamber 36b and a lower pressure chamber 36.
An end portion of the diaphragm 36a, which is partitioned into c, is in contact with the lower surface of the diaphragm 36a and has a stopper portion 36l that is enlarged in the radial direction. The displacement of the diaphragm 36a is transmitted to the valve body 32b via the temperature sensing rod 36f, and the stopper 36l is supported by the lower cover 36h so that the upper end 36k of the temperature sensing rod 36f slides in the lower pressure chamber 36c.

The collar member 40 is attached to the temperature sensitive rod 36f.
Are provided by, for example, press fitting, and the collar member 40
Is integrally formed of a large-diameter disk portion 40a and a small-diameter cylindrical portion 40b rising from one surface thereof, and is formed of a metal such as stainless steel or aluminum, and has a through hole 40c at the center. A temperature sensitive rod 36f is inserted into the through hole 40c, an O-ring 40d is arranged between the temperature sensitive rod 36f and the outer peripheral surface of the temperature sensitive rod 36f, and the disc portion 40a includes a lower pressure chamber 36c and a pressure equalizing hole 36c.
e is in contact with the stepped portion 30a of the valve body 30 formed between the valve body 30e and e, and is present in the lower pressure chamber 36c.
It is inserted in 6e.

Further, the step portion 30a of the valve body 30 has a small hole for communicating the lower pressure chamber 36c with the low pressure refrigerant passage 34,
For example, the bleed port 30b is formed in parallel with the temperature sensitive rod 36f.

According to this structure, even if the pressure in the low-pressure refrigerant passage 34 drops when the compressor is started, the collar member 40 exists in the lower pressure chamber 36c and the pressure equalizing hole 36e, so that the low-pressure refrigerant passage 34 and The collar member 40 blocks communication with the lower pressure chamber 36c, and the pressure drop in the low-pressure refrigerant passage 34 is transmitted to the lower pressure chamber 36c through the bleed port 30b. It is delayed by the port 30b and slowly transmitted to the lower pressure chamber 36c. Therefore, the pressure fluctuation in the upper pressure chamber 36b due to the pressure drop in the low-pressure refrigerant passage 34 is delayed and caused.
As a result, even when the compressor is started, the orifice 32 due to the displacement of the diaphragm 36a based on the rapid change in the pressure difference between the upper pressure chamber 36b and the lower pressure chamber 36c.
It is possible to avoid the sudden full open state of a, the flow rate of the refrigerant passing through the orifice 32a can be suppressed, and the refrigerant flow noise can be reduced. That is, the collar member 40 and the bleed port 30b act as means for delaying and transmitting the pressure fluctuation due to the pressure drop in the low pressure refrigerant passage 34 at the time of starting the compressor to the lower pressure chamber 36c and the upper pressure chamber 36b of the power element 36. The low pressure refrigerant passage 34
It acts as a means for avoiding the sudden full opening of the orifice 32a due to the pressure drop. Moreover, FIG.
In the embodiment shown in FIG. 2, the refrigerant flow noise can be reduced without significantly changing the configuration of the conventional expansion valve shown in FIG.

Although the embodiment has been described above, the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present invention. That is, in the present embodiment, in the expansion valve shown in FIG. 1, the collar member 40 is not limited to metal, but may be resin. Further, although the small hole has been described in the present embodiment, it goes without saying that the present invention is not limited to the small hole as long as it is a transmission means that delays and transmits the pressure fluctuation.

[0029]

According to the present invention, the pressure fluctuation of the pressure chamber in the power element due to the pressure drop of the low pressure refrigerant passage of the expansion valve at the time of starting the compressor can be delayed and caused, and therefore the abruptness of the orifice can be increased. Since full opening can be avoided, the refrigerant flow rate can be suppressed and the refrigerant flow noise can be reduced.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of an expansion valve of the present invention.

FIG. 2 is a cross-sectional view showing the configuration of a conventional expansion valve.

[Explanation of symbols]

30 valve body 30a step 30b bleed port 32a orifice 32b valve body 34 Low-pressure refrigerant passage 36 Power Element 36a diaphragm 36b Upper pressure chamber 36c Lower pressure chamber 36E Pressure equalizing hole 36f temperature sensitive stick 37f operating rod 40 color members 40a disk part 40b tube 40d O-ring

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tomoki Shimura             Setagaya-ku, Tokyo Todoroki 7-1724 shares             Ceremony company Fuji Kouki F term (reference) 3H057 AA04 BB45 CC07 DD04 DD05                       EE05 FC03 GG08 HH16 HH18

Claims (7)

[Claims] 1. A valve main body having therein a high-pressure side passage, a low-pressure side passage, an orifice communicating between these passages, a low-pressure refrigerant passage and a valve element opposed to the orifice, and a diaphragm. A power element provided outside the valve body having a pressure chamber, a temperature-sensitive drive rod that drives the valve element by displacement of the diaphragm according to pressure fluctuations in the pressure chamber, and the orifice by the valve element. In the expansion valve whose opening is controlled, the expansion valve is provided inside the valve body, which delay means delays a pressure fluctuation in the pressure chamber due to a pressure drop in the low-pressure refrigerant passage. 2. The delay means is a blocking member that is provided on the temperature-sensitive drive rod and blocks transmission of pressure, which is provided between the low-pressure refrigerant passage and the pressure chamber, and is provided inside the valve body. The expansion valve according to claim 1, wherein the expansion valve is a small hole that is formed to transmit the pressure drop in the low-pressure refrigerant passage to the pressure chamber. 3. The expansion valve according to claim 2, wherein the blocking member is a collar, and the small hole is a bleed port. 4. A valve main body having therein a high-pressure side passage, a low-pressure side passage, an orifice communicating between these passages, a low-pressure refrigerant passage and a valve body arranged to face the orifice, and a valve body. The valve element is driven by the displacement of a diaphragm that divides the power element provided outside the vehicle into a first pressure chamber in which a predetermined refrigerant is sealed and a second pressure chamber communicating with the low-pressure refrigerant passage. In the expansion valve including the temperature-sensitive drive rod, the temperature-sensitive drive rod is equipped with a blocking unit that blocks communication between the second pressure chamber and the low-pressure refrigerant passage, and the valve body includes: An expansion valve, wherein a small hole is formed to connect the second pressure chamber and the low-pressure refrigerant passage. 5. A high-pressure side passage and a low-pressure side passage through which the refrigerant flows toward the evaporator, an orifice communicating between these passages, a low-pressure refrigerant passage through which the refrigerant sent from the evaporator passes, and a valve element arranged opposite to the orifice. A valve body having therein and a power element provided outside the valve body, and the internal pressure changes according to the pressure and temperature of the refrigerant sent from the evaporator by the predetermined refrigerant enclosed in the power element. A diaphragm that partitions into a first pressure chamber and a second pressure chamber that communicates with the low-pressure refrigerant passage, a temperature-sensitive drive rod that is driven by displacement of the diaphragm, and urges the valve element toward the orifice side. The temperature-sensing rod causes the valve element to move toward and away from the orifice so as to control the flow rate of the refrigerant toward the evaporator. In the expansion valve to be controlled, an expansion valve is provided inside the valve body for avoiding a fully opened state of the orifice when the pressure in the low-pressure refrigerant passage decreases. 6. The avoidance means is a blocking means that is provided between the low pressure refrigerant passage and the second pressure chamber to prevent communication between the low pressure refrigerant passage and the second pressure chamber. The expansion valve according to claim 5, wherein the expansion valve is a small hole provided in the valve body for transmission to a chamber. 7. The blocking means is a collar member provided on the temperature sensitive drive rod, and the small hole is a bleed port provided substantially parallel to the temperature sensitive drive rod. The expansion valve according to item 6.