JPH08244446A - Refrigerating cycle of air conditioner for vehicle - Google Patents

Abstract

PURPOSE: To prevent the delivery pressure of a compressor at a high speed from becoming too high. CONSTITUTION: When a compressor 11 is rotated at a high speed, the delivery amount of refrigerant is increased, and the amount of refrigerant flowing through first and second refrigerant paths 12 and 13 is increased. Because the velocity of refrigerant at a restriction 19 becomes high, a pressure loss at the restriction 19 is increased, and the flow of refrigerant at a first condenser 14 becomes larger than that at a second condenser 15. Also, because the first condenser 14 is located on the upstream side of cooling air and has high cooling capacity, a condensing temperature as well as condensing pressure can be prevented from rising though the degree of super cooling is lowered, and the delivery pressure of the compressor 11 is not increased too high.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerating cycle for a vehicle air conditioner in which a cooling capacity is improved by supercooling a refrigerant.

[0002]

2. Description of the Related Art One of the methods for improving the cooling capacity of a refrigeration cycle is to increase the enthalpy difference before and after evaporation of the refrigerant in an evaporator by giving the refrigerant a supercooling degree at the inlet of an expansion valve. There is. The applicant of the present invention has previously described the configuration of a condenser for carrying out this method in Japanese Patent Application No. 4-162.
The application was filed as No. 508 (JP-A-6-2970).

As shown in FIG. 6, the first and second condensers 1 and 2 having the same shape are arranged in the cooling air blowing passage in front of and behind the blowing direction indicated by arrow A. However, since the first condenser 1 on the leeward side is cooled better than the second condenser 2 on the leeward side, the supercooled refrigerant from the first condenser 1 passes through the expansion valve 3 through the expansion valve 3. The refrigerant in the saturated liquid state is supplied from the second condenser 2 to the evaporator 5 and is supplied to the evaporator 5.
After being temporarily stored in the evaporator 4, it is supplied to the evaporator 4 through the expansion valve 3.

[0004]

In the refrigerating cycle of FIG. 6, the first and second condensers 1 and 2 having the same shape, that is, those having substantially the same flow path resistance are used. Even if the amount of discharged refrigerant changes as the number of revolutions of 6 changes, almost the same amount of refrigerant flows through the first and second condensers 1 and 2. On the other hand, with respect to the condensing capacity, the first condenser 1 existing on the leeward side is superior to the second condenser 2 existing on the leeward side, so that the refrigerant is the second condenser 2 In the first condenser 1, condensation is completed before reaching the refrigerant outlet, and further cooling is further performed between the first condenser 1 and the refrigerant outlet. It is a state.

However, in this device, when the number of revolutions of the compressor 6 increases and the amount of discharged refrigerant increases, the second condenser 2 having a low condensing capacity and the first condenser 1 having a good condensing capacity are also provided.
Since the same amount of refrigerant must be condensed, the condensing temperature becomes high, and on the other hand, in the first condenser 1 having excellent condensing ability, the degree of supercooling of the refrigerant becomes significantly high. The condensing capacity of the entire device decreases, and the discharge pressure of the compressor 6 increases. Therefore, the compressor 6
It is necessary to make the seal structure with high pressure resistance and high accuracy, which is disadvantageous in terms of cost. Further, there is a problem that a safety device, for example, a pressure switch for detecting the discharge pressure of the compressor 6 or a temperature switch for detecting the temperature of the discharged refrigerant is activated early to stop the operation, resulting in cooling failure. .

The present invention has been made in view of the above circumstances. An object of the present invention is, even if the amount of refrigerant discharged from a compressor increases.
(EN) A refrigeration cycle for a vehicle air conditioner capable of preventing a decrease in the condenser capacity of the entire condenser and a rise in the discharge pressure of a compressor.

[0007]

In order to achieve the above object, the present invention is provided with first and second refrigerant passages connected in parallel to a compressor, and in the first refrigerant passage. A first condenser, a second condenser provided in the second refrigerant passage, and a liquid receiver provided in the second refrigerant passage and receiving refrigerant from the second condenser. And a second refrigerant passage having, wherein the first condenser is arranged on the windward side of the second condenser in a cooling air blowing passage,
It is characterized in that resistance increasing means is provided for making the flow resistance of the second refrigerant passage larger than the flow resistance of the first refrigerant passage (claim 1).

In this case, the resistance increasing means is the second
The flow passage resistance of the cooling pipe forming the refrigerant passage of the condenser may be made larger than the flow passage resistance of the cooling pipe forming the refrigerant passage of the first condenser (claim 2). The resistance increasing means is preferably throttle means provided on the refrigerant outlet side of the liquid receiver (Claim 3). At this time, the throttle means is a variable throttle whose opening degree changes. (Claim 4).

Further, it is preferable that the variable throttle is configured to change its opening degree according to the load of the compressor (claim 5). The first and second condensers are
It is preferable that they are formed in the same shape (claim 6).

[0010]

According to the means of the first aspect, when the amount of discharged refrigerant increases due to an increase in the number of revolutions of the compressor or an increase in thermal load, the flow rate of the refrigerant flowing through the first refrigerant passage and the second refrigerant passage increases. As a result, the refrigerant flow velocity also increases. When the flow velocity of the coolant increases, the pressure loss of the coolant flowing through the first and second coolant passages increases. At this time, the second
Since the flow passage resistance of the refrigerant passage is greater than the flow passage resistance of the first refrigerant passage, the pressure loss of the refrigerant flowing through the second refrigerant passage is smaller than the pressure loss of the refrigerant flowing through the first refrigerant passage. Also grows. Therefore, when the amount of refrigerant discharged from the compressor increases, the amount of refrigerant flowing into the first refrigerant passage becomes larger than the amount of refrigerant flowing into the second refrigerant passage,
The refrigerant flow rate of the first condenser on the windward side is higher than the refrigerant flow rate of the second condenser. Therefore, a larger amount of refrigerant is condensed in the first condenser having excellent condensing capacity, and a relatively small amount of refrigerant is condensed in the second condenser having low condensing capacity, so that the entire condenser is condensed. The capacity is improved and the rise of the discharge pressure of the compressor is suppressed.

According to the second aspect of the present invention, the number of parts is reduced by setting the flow passage resistance of the cooling pipe of the second condenser to be larger than that of the cooling pipe of the first condenser. The flow resistance of the second refrigerant passage can be made larger than the flow resistance of the first refrigerant passage without increasing. According to the means of claim 3, the flow passage resistance of the second refrigerant passage is made larger than the flow passage resistance of the first refrigerant passage with a simple configuration in which the throttle means is provided on the refrigerant outlet side of the liquid receiver. You can

According to the fourth aspect of the present invention, the throttle means is a variable throttle so that the flow passage resistance of the second refrigerant passage is adjusted according to various conditions such as the flow velocity and temperature of the cooling air, And the refrigerant can be distributed to the second condenser in an optimal ratio. In the means according to claim 5, since the variable throttle is configured so that its opening degree is changed according to the load of the compressor, the second refrigerant is changed according to the amount of refrigerant discharged from the compressor, the temperature of the discharged refrigerant, and the like. Adjusting the flow path resistance of the passage, the first and second
It is possible to distribute the refrigerant to the condenser in the optimum ratio.
In the means described in claim 6, since the first and second condensers are formed in the same shape, they can be configured easily and inexpensively.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. 1 to 3 by applying it to a refrigeration cycle of an air conditioner for an automobile. FIG. 1 shows a schematic configuration of a refrigeration cycle. A compressor 11 is configured to be driven by an automobile engine via an electromagnetic clutch (not shown), and a discharge port 11 a of the compressor 11 is connected to the compressor 11. The first and second refrigerant passages 12 and 13 are connected in parallel.

A first condenser 14 is provided in the first refrigerant passage 12, and a second condenser 15 and a liquid refrigerant from the second condenser 15 are provided in the second refrigerant passage 13. A receiver 16 is provided for receiving the liquid. The refrigerant outlet side of the first and second refrigerant passages 12 and 13, that is, the first
The refrigerant outlet of the condenser 14 and the refrigerant outlet of the liquid receiver 16 are connected to each other and connected to the refrigerant inlet of the expansion valve 17 as expansion means by piping. The refrigerant outlet of the expansion valve 17 is connected to the refrigerant inlet of the cooler 18, and the cooler 18
The refrigerant outlet is connected to the suction port 11b of the compressor 11 by piping.

The above-mentioned first and second condensers 14 and 1
5 have the same shape, so that both condensers 14,
The cooling pipes for the 15 refrigerants have the same length and the same flow path resistance. Such first and second condensers 14
And 15 are arranged side by side so that the first condenser 14 is located on the windward side in the blowing passage of the cooling air that is sent in the direction indicated by the arrow A by the cooling fan provided in the engine room of the automobile. ing. Thereby, the first condenser 14 can obtain a higher cooling effect than the second condenser 15.

A throttle 19 as a throttle means is provided on the refrigerant outlet side of the liquid receiver 16 in the second refrigerant passage 15.
Is provided. As shown in FIG. 2, for example, this throttle 19 is configured by having two stages of in-pipe orifices 19a and 19b, and is located on the downstream side of the first orifice 19a on the upstream side with respect to the flow direction of the refrigerant indicated by the arrow B. The second orifice 19b has a larger degree of throttling. Since the throttle 19 is provided in the second refrigerant passage 14, the passage resistance of the second refrigerant passage 14 is larger than the passage resistance of the first refrigerant passage 13. The restriction 19 may have only one in-tube orifice.

Next, the operation of the refrigeration cycle configured as described above will be described. Compressor 1 by an engine not shown
1 is driven, the gas refrigerant compressed by the compressor 11 is split into the first and second refrigerant passages 12 and 13 connected in parallel, and the first and second condensers 14 are connected.
And fifteen. The gaseous refrigerant that has flowed into the first and second condensers 14 and 15 is cooled and condensed by cooling air sent from a cooling fan (not shown). At this time, since the first condenser 14 located on the leeward side has better cooling performance and better condensing ability than the second condenser 15 on the leeward side, the gas refrigerant flowing into the first condenser 14 is A saturated liquid is formed on the way to the refrigerant outlet, and then is further cooled in the process of reaching the refrigerant outlet to be in a supercooled state and flows out as a liquid refrigerant having a degree of supercooling. On the other hand, the gaseous refrigerant flowing into the second condenser 15 on the leeward side becomes a saturated liquid refrigerant near the refrigerant outlet and is stored in the liquid receiver 16.
Then, the liquid receiver 16 separates gas and liquid, and only the saturated liquid refrigerant flows out.

The supercooled liquid refrigerant sent from the first condenser 14 and the saturated liquid refrigerant sent from the liquid receiver 16 join together on the way to the expansion valve 17, and the first refrigerant is introduced at the refrigerant inlet of the expansion valve 17. The supercooled liquid refrigerant from the condenser 14 and the saturated liquid refrigerant from the liquid receiver 16 are mixed. The mixed liquid refrigerant has an intermediate value between the supercooled liquid refrigerant and the saturated liquid refrigerant as a supercooling degree, but as a result, it becomes a liquid refrigerant having a supercooling degree, and the supercooled liquid refrigerant is an evaporator. The air inside the vehicle, which is the air to be conditioned, evaporates at 18, and cools around the evaporator 18. After that, the evaporated refrigerant is sucked into the compressor 11, compressed by the compressor 11, and then split into the first and second refrigerant passages 12 and 13 again.

By the way, when the engine speed increases, the compressor 11 speed also increases, so that the refrigerant discharge amount increases. At this time, assuming that the throttle 19 is not provided, the first refrigerant passage 12 and the second refrigerant passage 13
Since the flow path resistances of the two refrigerant passages 12 and 1 are the same,
An equivalent large amount of refrigerant flows into 3. Then, although the degree of supercooling in the first condenser 14 becomes high, the condensing temperature and thus the condensing pressure become high in the second condenser 15 having a low condensing capacity.

However, in the present embodiment in which the throttle 19 is provided, when the liquid refrigerant from the liquid receiver 16 passes through the orifices 19a and 19b of the throttle 19, pressure loss is caused and the pressure thereof is reduced. Part of the liquid refrigerant evaporates to generate bubbles. Then, in the liquid refrigerant flowing through the throttle 19, a flow path resistance loss due to the bubbles occurs. In this case, as the flow rate of the refrigerant increases, the speed of the refrigerant flowing through the throttle 19 increases, so that the pressure drop when passing through the orifices 19a and 19b increases and the flow path resistance loss increases.
This means that as the amount of refrigerant discharged from the compressor 11 increases, the rate of increase in the flow path resistance loss of the second refrigerant passage 13 becomes first.
Of the refrigerant passage 12 is larger than the increase rate of the flow resistance loss of the refrigerant passage 12. As a result, as the amount of refrigerant discharged from the compressor 11 increases, the first amount relative to the amount of refrigerant discharged from the compressor 11 increases. The ratio of the flow rate of the refrigerant in the refrigerant passage 12 will increase.

Therefore, as the amount of refrigerant discharged from the compressor 11 increases, the first and second refrigerant passages 12 and 1
3, the amount of refrigerant flowing into the third condenser 14 and the first and second condensers 14
Although the amount of refrigerant flowing into and 15 increases, the refrigerant flow rate to the first condenser 14 becomes larger than the refrigerant flow rate to the second condenser 15. At this time, since the first condenser 14 is on the windward side and has an excellent condensing capacity, even if more refrigerant flows in, the degree of supercooling is reduced, but the gas refrigerant is changed to the liquid refrigerant in the supercooled state. Or a saturated liquid refrigerant near the refrigerant outlet. On the other hand, although the second condenser 15 is on the leeward side and has a low condensing capacity, the flow rate of the refrigerant is small, so that the second condenser 15 can be a saturated liquid refrigerant without causing a significant increase in the condensing temperature and thus the condensing pressure.

As described above, when the compressor 11 rotates at a high speed, the flow rate of the refrigerant to the first condenser 14 having an excellent condensing capacity is made larger than the flow rate of the refrigerant to the second condenser 15 to condense the entire condenser. It is possible to obtain an excellent effect that the discharge pressure of the compressor 11 can be suppressed to the utmost by increasing the pressure. Note that when the compressor 11 rotates at a high speed, the degree of supercooling of the refrigerant flowing into the evaporator 18 is lower than when the compressor rotates at a low speed, but the required cooling capacity can be sufficiently secured by increasing the amount of refrigerant discharged from the compressor 11. It is a thing.

In FIG. 3, the rotational speed of the compressor 11 is 2000r.
Refrigerant flow rate ratio Gr of the first condenser 14 in pm (constant)
By changing the condensation capacity, the degree of supercooling, the discharge pressure of the compressor 11,
The results of experiments on cooling capacity are shown. Here, the refrigerant flow ratio Gr is the first with respect to the amount of refrigerant discharged from the compressor 11.
Is the ratio of the refrigerant flow rate of the condenser 14 (refrigerant flow rate of the first condenser 14 / discharged refrigerant amount of the compressor 11). The condensing capacity is the total condensing capacity of the first and second condensers 14 and 15, and the degree of supercooling is the supercooled liquid refrigerant from the first condenser 14 and the saturation from the second condenser 15. The value is shown after the liquid refrigerant is merged.

As is clear from the figure, the refrigerant flow ratio Gr
Is 0.5, that is, the throttle 19 is not provided, the flow resistances of the first and second refrigerant passages 12 and 13 are made equal, and an equal amount of refrigerant is supplied to the first and second condensers 14 and 15. When it is made to flow in, the cooling capacity close to the maximum can be obtained, but the discharge pressure of the compressor 11 is high due to the high degree of supercooling. On the other hand, the refrigerant flow ratio G
When the throttle 19 having the flow path resistance such that r is 0.54 is provided, the maximum cooling capacity can be obtained, and the discharge pressure of the compressor 11 is reduced due to the lower supercooling degree. .
Further, when the flow path resistance throttle 19 having the refrigerant flow rate ratio Gr of 0.64 is provided, the cooling capacity decreases, but the condensing capacity increases, and the discharge pressure of the compressor 11 further decreases. , About 0.1 MPa lower than that when the refrigerant flow rate ratio Gr is 0.5.

By providing such a throttle 19, the refrigerant flow ratio G
As will be understood from the above explanation, the degree of supercooling and the decrease in discharge pressure that occur when r exceeds 0.5 become larger as the rotational speed of the compressor 11 increases.
Therefore, when there is no margin in the discharge pressure of the compressor 11 and it is necessary to suppress this, by providing the throttle 19 of the flow path resistance according to the allowable discharge pressure, the discharge pressure of the compressor 11 during high speed rotation is increased. It is possible to prevent the pressure from exceeding the allowable pressure.

As described above, according to this embodiment, the liquid receiver 16
A throttle 19 is provided on the refrigerant outlet side of the compressor so that the passage resistance of the second refrigerant passage 13 becomes larger than the passage resistance of the first refrigerant passage 12 by the throttle 19. In this case (when the load is low), the refrigerant flow rate of the first condenser 14 is made as close as possible to the refrigerant flow rate of the second condenser 15 (actually, the refrigerant flow rate of the first condenser 14 is The cooling capacity of the first condenser 11 is higher than that of the second condenser 15 when the compressor 11 rotates at high speed (high load). So that more refrigerant can flow into the condenser 14 and the total condensing capacity of the first and second condensers 14 and 15 is increased so that the discharge pressure of the compressor 11 does not exceed the allowable pressure. be able to. Therefore, the compressor 11
The sealing structure does not have to have high withstand pressure and high accuracy, and can be cost-effective.

In the present embodiment, the first and second condensers 14 and 15 having the same general shape are used, and the first condenser 14 is arranged on the windward side of the cooling air to prevent the refrigerant from passing therethrough. Since the cooling degree is provided, a simple and inexpensive refrigeration cycle can be configured without separately manufacturing a condenser for supercooling. Moreover, the flow passage resistance of the second coolant passage 13 can be made larger than the flow passage resistance of the first coolant passage 12 with a simple configuration in which the throttle 19 is provided on the coolant outlet side of the liquid receiver 16, which is inexpensive. Can be configured to.

FIG. 4 shows a second embodiment of the present invention.
The same parts as those in FIG. 1 are designated by the same reference numerals and only different parts will be described. In this embodiment, a variable diaphragm 20 is provided instead of the diaphragm 19 of the first embodiment. The variable throttle 20 is composed of a flow rate adjusting valve or the like, and uses, for example, a motor as a drive source for adjusting the opening degree. On the other hand, the discharge port 11a of the compressor 11 and the first and second refrigerant passages 12 and 13
A pressure sensor 22 that detects the discharge pressure of the compressor 11 is provided in the discharge pipe 21 that connects between and. In addition,
Since the discharge pressure of the compressor 11 is proportional to the load of the compressor 11, the pressure sensor 22 functions as a load sensor that is a load detecting unit that detects the load of the compressor 11. And
The output signal of the pressure sensor 22 is input to control means, for example, a control device 23 mainly composed of a microcomputer, and the control device 23 controls the variable throttle 20 according to the discharge pressure of the compressor 11 detected by the pressure sensor 22. Adjust the opening (flow path resistance).

In this case, the discharge pressure of the compressor 11 is divided into a plurality of ranges within a certain range, and the optimum opening of the variable throttle 20 corresponding to each of the divided pressure ranges is experimentally obtained. The relationship between the range and the rotational position of the opening adjusting motor for achieving the optimum opening is stored as data in a memory (not shown) of the control device 23.
3 reads out the rotational position of the opening adjusting motor corresponding to the discharge pressure detected by the pressure sensor 22 from the data and controls the rotational position of the opening adjusting motor. The opening is adjusted according to.

When the variable diaphragm 20 is used as described above,
Depending on the load of the compressor 11, the first and second condensers 14
And 15 refrigerant flow rates can be controlled. For example, when the load is low (during idling), the opening of the variable throttle 20 is increased so that the flow resistance of the second refrigerant passage 13 is smaller than the flow resistance of the first refrigerant passage 12,
The refrigerant flow rate to the first condenser 14 is made smaller than the refrigerant flow rate to the second condenser 15 to increase the degree of supercooling of the refrigerant so that a high cooling capacity can be obtained and a high load is applied. At the time of high speed rotation, the opening of the variable throttle 20 is reduced to reduce the flow resistance of the second refrigerant passage 13 to the first refrigerant passage 12
The flow rate of the refrigerant to the first condenser 14 is made smaller than the flow rate of the refrigerant to the second condenser 15 to reduce the degree of supercooling, thereby reducing the discharge pressure of the compressor 11. Therefore, the refrigerant flow rates of the first and second condensers 14 and 15 can be controlled according to the load of the compressor 11.

Compressor 11 when such control is performed
5 shows the relationship among the load, the supercooling degree, the discharge pressure of the compressor 11, and the cooling capacity. In the figure, the solid line shows the case of the present invention, and the broken line shows the conventional one. As is clear from the figure, it is understood that when the load is low, the degree of supercooling can be increased, and when the load is high, the degree of subcooling can be decreased to suppress the discharge pressure.

The present invention is not limited to the embodiments described above and shown in the drawings, and the following expansions and modifications are possible. By making the flow path resistance of the second condenser 15 larger than the flow path resistance of the first condenser 14 (resistance increasing means) without providing a throttle, the flow path resistance of the second refrigerant passage 13 is increased. It may be configured to be larger than the flow resistance of the first refrigerant passage 12. In this case, the second
As a concrete means for making the flow path resistance of the condenser 15 of the first condenser 14 larger than the flow path resistance of the first condenser 14, a large number of aluminum cooling cups having a circular cross section having a hollow passage as a refrigerant passage are cooled. In the case of a fin-tube type condenser configured by passing through fins, the cooling pipe of the second condenser 15 is made thinner than the cooling pipe of the first condenser 14, and the hollow interior is partitioned to form a plurality of refrigerant passages. In the case of a corrugated fin type condenser configured by attaching corrugated fins to the flat cooling tube forming the above, the number of refrigerant passages in the cooling tube of the second condenser 15 is set to the refrigerant in the cooling tube of the first condenser 14. It is possible to reduce the number of passages. When the flow path resistance of the second condenser 15 is set to be larger than that of the first condenser 14 as described above, no restriction is required, the number of parts is reduced, and the number of assembly steps is increased. There is nothing to do.

The temperature of the refrigerant discharged from the compressor 11, the number of revolutions of the compressor 11, the amount of refrigerant discharged from the compressor 11, the speed of the automobile, the temperature, etc. are detected, and the variable throttle 20 is opened according to the detection results. The degree may be changed. In particular, since the speed of the vehicle detects the speed of the cooling air flowing around the condensers 14 and 15, and the air temperature detects the temperature of the cooling air, when the opening of the variable throttle 20 is changed accordingly. The cooling air condition, that is, the condenser 14,
Therefore, the opening degree of the variable throttle 20 can be controlled according to the condensing capacity of 15.

[Brief description of drawings]

FIG. 1 is a refrigeration cycle configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a sectional view of a diaphragm

[Fig. 3] Refrigerant flow rate ratio and condensation capacity, supercooling degree, discharge pressure,
Diagram showing the relationship with cooling capacity

FIG. 4 is a view corresponding to FIG. 1 showing a second embodiment of the present invention.

FIG. 5 is a diagram showing a relationship among a load, a supercooling degree, a discharge pressure, and a cooling capacity.

FIG. 6 is a view corresponding to FIG. 1 showing a conventional example.

[Explanation of symbols]

11 is a compressor, 12 and 13 are first and second refrigerant passages, 1
Reference numerals 4 and 15 are first and second condensers, 16 is a liquid receiver, 18 is a cooler, 19 is a throttle (resistance increasing means), and 20 is a variable throttle (resistance increasing means).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukihiro Ishii 1-1, Showa-cho, Kariya city, Aichi prefecture Nihon Denso Co., Ltd. (72) Inventor Hidemasa Takahashi 1-1-cho, Showa town, Kariya city, Aichi prefecture Nidec Within the corporation

Claims (6)

[Claims] 1. A first and second refrigerant passages connected in parallel to a compressor, a first condenser provided in the first refrigerant passage, and a second refrigerant passage in the second refrigerant passage. A second condenser provided in the second refrigerant passage, and a liquid receiver that is provided in the second refrigerant passage and receives the refrigerant from the second condenser. In the ventilation passage of the second
Is provided on the windward side of the condenser, and resistance increasing means is provided for making the flow path resistance of the second refrigerant passage larger than the flow path resistance of the first refrigerant passage. A refrigeration cycle for a vehicle air conditioner. 2. The resistance increasing means has a flow path resistance of a cooling pipe forming a refrigerant passage of the second condenser, which is higher than a flow path resistance of a cooling pipe forming a refrigerant passage of the first condenser. The refrigeration cycle of the vehicle air conditioner according to claim 1, wherein the refrigeration cycle is increased. 3. The refrigeration cycle for a vehicle air conditioner according to claim 1, wherein the resistance increasing means is a throttle means provided on the refrigerant outlet side of the liquid receiver. 4. The refrigeration cycle for a vehicle air conditioner according to claim 3, wherein the throttle means is a variable throttle whose opening degree changes. 5. The refrigeration cycle for a vehicle air conditioner according to claim 4, wherein the variable throttle is configured to change an opening degree according to a load of the compressor. 6. The refrigeration cycle for a vehicle air conditioner according to claim 1, wherein the first and second condensers have the same shape.