Refrigeration – With vehicle feature – Occupant-type vehicle
Reexamination Certificate
2001-04-05
2002-06-04
Tapolcai, William E. (Department: 3744)
Refrigeration
With vehicle feature
Occupant-type vehicle
C062S527000
Reexamination Certificate
active
06397616
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application is based on and incorporates herein by reference Japanese Patent Application Nos. 2000-105276 filed on Apr. 6, 2000, 2000-189600 filed on Jun. 23, 2000, and 2000-337838 filed on Nov. 6, 2000.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a pressure reducer in a refrigeration cycle unit suitable for use in a vehicle air-conditioner.
2. Description of Related Art
A temperature type pressure reducer has been normally used as a pressure reducer to automatically control the flow rate of refrigerant so that the degree of superheat of refrigerant at the output of an evaporator is maintained at a predetermined value because the width of fluctuations of cycle operating condition is large in a vehicular air-conditioning refrigeration cycle unit. However, the structure of the temperature pressure reducer is complicated and is expensive because it requires a valve driving mechanism which operates corresponding to the degree of superheat of the refrigerant at the output of the evaporator.
Then, there has been proposed a pressure reducer having a simple structure by eliminating the valve driving mechanism in JP-A-11-257802. In this prior art, a pressure reducer having a valve mechanism for changing a restrict diameter corresponding to differential pressure (difference between high pressure and low pressure of the cycle) before and after the pressure reducer is constructed as shown in
FIG. 22
in a refrigeration cycle unit. In the accumulator type refrigeration cycle unit, an accumulator for collecting liquid refrigerant by separating gas and liquid of the refrigerant is disposed between the outlet of the evaporator and the suction side of the compressor.
According to the prior art, the valve mechanism expands the restrict diameter when the circulating flow rate of the cycling refrigerant is balanced with the radiating capability of the condenser and the differential pressure is smaller than a first predetermined value P
1
in running normally for example. Then, the valve mechanism reduces the restrict diameter when the radiating capability of the condenser drops due to the reduction of the cooling air amount and the high pressure increases, thus increasing the differential pressure more than the first predetermined value P
1
in idling. Then, the valve mechanism expands the restrict diameter again when the flow rate of the cycling refrigerant rises remarkably due to the high-speed rotation of the compressor in running at high-speed for example and the high pressure rises further, thereby increasing the differential pressure more than a second predetermined value P
2
.
Thus, the valve mechanism lowers the low pressure by reducing the restrict diameter in idling to assure the cooling capability in idling and expands the restrict diameter in running at high-speed to prevent the high pressure from rising abnormally in the prior art.
However, the actual relationship between the refrigeration cycle operating condition and the differential pressure (difference of high pressure and low pressure in the cycle) before and after the pressure reducer is not determined uniquely as shown in FIG.
22
. For instance, there is a case when the high pressure rises and the differential pressure becomes greater than the second predetermined value P
2
when the radiating capability of the condenser drops extremely even in idling when the outside temperature is high or when the traffic jam occurs in a city and the valve mechanism expands the restrict diameter similarly to the case of running at high-speed. As a result, there arise problems that the low pressure (refrigerant evaporating temperature) rises and the subcooling degree of the refrigerant at the outlet of the condenser reduces, thereby dropping the cooling capability.
A vehicular transmission gear is shifted to low-speed gear and the flow rate of the cycling refrigerant rises remarkably due to the high-speed rotation of the compressor in running an uphill road even in running normally. However, since the car speed is low in running the uphill road, it is often unable to obtain the cooling air amount of the condenser corresponding to the rise of the flow rate of the refrigerant. As a result, there is a case when the high pressure rises and the differential pressure becomes greater than the first predetermined value P
1
as the radiating capability of the condenser becomes insufficient. The valve mechanism reduces the restrict diameter similarly to the case in idling at this time. Thereby, the high pressure rises further, thereby increasing the driving power of the compressor and worsening the efficiency of the cycle.
SUMMARY OF THE INVENTION
In view of the problems described above, an object of the present invention is to provide a pressure reducer having the small and simple structure and capable of controlling the flow rate of refrigerant favorably even when the operating condition fluctuates widely.
In the accumulator type refrigeration cycle unit in which an accumulator for collecting liquid refrigerant by separating the gas and liquid of the refrigerant is disposed between the outlet of the condenser and the intake side of the compressor as disclosed in JP-A-11-257802, saturated gas refrigerant is taken in from the accumulator and is compressed and discharged. Then, the condition (subcooling degree or dryness) of the refrigerant at the outlet of the condenser changes due to the fluctuations of the cycle operating condition. It is effective to maintain the subcooling degree of the refrigerant at the outlet of the condenser in an adequate range (around 7-15° C.) in order to improve the efficiency of the refrigeration cycle.
That is, when the subcooling degree of the refrigerant at the outlet of the condenser becomes excessively large, the driving power of the compressor increases due to the rise of the high pressure. When the subcooling degree of the refrigerant at the outlet of the condenser becomes excessively small in contrary, the difference of enthalpy between the inlet and outlet of the evaporator decreases, thus dropping the capability.
Then, the present invention achieves the above-mentioned object by favorably controlling the flow rate of refrigerant with respect to the wide fluctuations of the driving condition while maintaining the subcooling degree of the refrigerant at the outlet of the condenser in the appropriate range.
According to a first aspect of the present invention, variable restrict means is disposed at the upstream side of flow of the refrigerant. Fixed restrict means is disposed at the downstream side of the variable restrict means, and refrigerant which has passed through the variable restrict means always flows thereto. An intermediate space is provided between said variable restrict means and the fixed restrict means, and passage sectional area of which is larger than that of the fixed restrict means. The length of the intermediate space is larger than a predetermined length required for allowing the refrigerant injected out of the variable restrict means to expand more than a passage sectional area of the fixed restrict means.
The fixed restrict means has the shape of a nozzle or the like. The change of flow rate is large, i.e., a flow rate control gain is large, in the area B where the dryness of refrigerant is small (dryness x<0.1 for example) as indicated by a dot chain line (1) in
FIG. 3
described later.
Then, noticing on this point, the variable restrict means disposed at the upstream side of the flow of refrigerant decompresses the subcool liquid refrigerant at the outlet of the condenser by a predetermined degree to change to the small dryness area, the gas-liquid two phase refrigerant in the small dryness area is flown into the fixed restrict means to decompress again.
Thereby, the refrigerant flow rate control action can be performed in the refrigerant state in which the flow rate control gain is large by the fixed restrict means, so that a large refrigerant flow rate control width D (
FIG. 5
) can be obtained by
Hotta Teruyuki
Inaba Atsushi
Ito Shigeki
Yamanaka Yasushi
Yamasaki Kurato
Denso Corporation
Harness Dickey & Pierce PLC
LandOfFree
Pressure reducer and refrigerating cycle unit using the same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Pressure reducer and refrigerating cycle unit using the same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Pressure reducer and refrigerating cycle unit using the same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2921812