Vehicular air conditioner

Details Vehicular air conditioner Vehicular air conditioner

1999-06-07

2001-05-22

Tanner, Harry B. (Department: 3744)

Refrigeration

Automatic control

Refrigeration producer

C062S228500, C062S323400

Reexamination Certificate

active

06233957

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vehicular air conditioner for controlling discharge temperature using a demand capacity change compressor.
2. Description of the Related Art
FIG. 4
shows a schematic construction of a conventional vehicular air conditioner. This vehicular air conditioner is an example of one installed in a standard automobile.
An air conditioning unit
10
for effecting cooling, heating or dehumidifying of introduced air and then discharging the air to a vehicle cabin comprises; an inside air/outside air box
10
A, a blower unit
10
B, a cooler unit
10
C and a heater unit
10
D. The air conditioning unit
10
is normally installed in a vehicle cabin under the dashboard. Moreover, numeral
11
denotes a control section for controlling various operations, and
12
denotes an operation section in which is arranged various switches which can be set up and operated according to the preference of a passenger, and an operation display section.
As follows is a brief description of the air conditioning unit
10
in air flow direction sequence.
Air introduced into the air conditioning unit
10
is selected from either outside air “a” outside of the vehicle cabin or inside air “b” inside of the vehicle cabin, by opening or closing an inside air/outside air changeover damper
13
in the inside air/outside air box
10
A. Introduced outside air “a” or inside air “b” (hereinafter referred to as “introduced air”) is drawn in by a blower fan
14
provided in the blower unit
10
B, or as vehicle traveling wind, passed through an air conditioning duct AD and then sent to an evaporator
15
in the cooler unit
10
C installed on the downstream side of the blower fan
14
. To this evaporator
15
is supplied a low temperature and low pressure liquid refrigerant from a refrigerant system which forms a refrigerating cycle at the time of a cooling and dehumidifying operation, effecting cooling and dehumidifying by exchanging heat with the introduced air passing through the evaporator
15
.
The refrigerant system is composed mainly of a compressor
16
, a condenser
17
, an expansion valve
18
and the evaporator
15
, and a refrigerant circulating circuit is formed by connecting each unit with refrigerant piping
19
.
The compressor
16
is connected via a compressor clutch
20
to an engine E as a drive source. The compressor
16
compresses a low temperature and low pressure gas refrigerant gasified by the evaporator
15
, and supplies this to the condenser
17
as a high temperature and high pressure gas refrigerant.
The condenser
17
cools the high temperature and high pressure gas refrigerant supplied from the compressor
16
with outside air, such as traveling wind to condense and liquefy the gaseous refrigerant. The refrigerant liquefied in this way is separated into gas and liquid by a receiver (not shown), and then supplied to the expansion valve
18
as a high temperature and high pressure liquid refrigerant.
The expansion valve
18
decompresses and expands the high temperature and high pressure liquid refrigerant to give a low temperature and low pressure liquid (mist) refrigerant, and supplies the liquid refrigerant to the evaporator
15
installed in the air conditioning unit
10
.
Hereafter, by circulating the refrigerant in the same manner, the refrigerating cycle is formed.
On the downstream side of the evaporator
15
, a heater unit
10
D is provided in a prescribed location, and a heater core
21
is installed therein. To this heater core
21
is introduced a high temperature engine coolant for which the flow rate is controlled by a water valve
22
, effecting heating by exchanging heat with the passing introduced air. Moreover, the flow rate of the introduced air passing through the heater core
21
can be adjusted by the opening of an air mix damper
22
.
As a result, introduced air can be adjusted to a predetermined temperature in the heater unit
10
D, or air-conditioned air can be blown selectively by the damper operation from a defroster air outlet
23
, a face air outlet
24
and a foot air outlet
25
provided in the heater unit
10
D.
Such an air conditioning unit
10
is so constructed that the heater core
21
for effecting heating is arranged on the downstream side of the evaporator
15
which effects cooling and dehumidifying, enabling dehumidifying air conditioning where cooled and dehumidified introduced air is heated again to a suitable temperature. There is thus the merit that the temperature can be maintained and condensation on the window can be cleared.
Particularly, in an electric car or a hybrid car (using both an electric motor and an internal combustion engine as a drive source), a heat pump type air conditioner is adopted, since there is the case where no engine coolant is obtained as a heat source for heating, or the engine coolant is insufficient. In this case, a four way valve is arranged in the refrigerating cycle to reverse the refrigerant flow direction for the heating operation and for the cooling operation. Consequently, at the time of the heating operation, the above described evaporator
15
operates as a condenser, and the condenser
17
operates as an evaporator. As a result, the vehicle cabin can be heated with heat drawn from the outside air.
With the above described conventional vehicular air conditioner, since the compressor
16
is driven using the engine E as a drive source, the capacity thereof varies largely depending upon the traveling condition of the vehicle. That is to say, the discharge pressure HP and the suction pressure LP vary depending upon fluctuations in engine RPM. Consequently, since the cooling capacity of the refrigerating cycle increases substantially linearly in proportion to the RPM of the engine E, then in many cases, the cooling capacity does not meet the demand on the air conditioner side.
Therefore, with a conventional vehicular air conditioner, the cooling capacity is adjusted by switching the compressor clutch
20
ON/OFF, or cool air and warm air are mixed by making high temperature engine coolant flow into the heater core
21
to obtain a mild discharge temperature.
There is thus a problem in that a shock caused at the time of switching the clutch ON/OFF impairs the traveling feeling, or that variations in the discharge temperature impairs the air conditioning feeling. Moreover, there is another problem in that the method of mixing cool air and warm air to adjust the discharge temperature causes a needless energy loss, which goes against the recent trend of energy saving.
SUMMARY OF THE INVENTION
In view of the above situation, it is an object of the present invention to provide a vehicular air conditioner which is not influenced by fluctuations in engine RPM, and which can give good air conditioning feeling with low energy consumption.
The present inventors have focused on the fact that the suction pressure (low pressure) of the refrigerating cycle has a fixed relation to discharge temperature, and have realized a constant discharge temperature by using a demand capacity change compressor in a vehicular air conditioner of the present invention.
The demand capacity change compressor adopted herein is obtained by combining, for example, a “capacity control device for a compressor” described in U.S. Pat. No. 4,886,425 with a “capacity control device for a compressor” described in Japanese Utility Model Application, First Publication No. Sho 64-56588.
The “capacity control device for a compressor” described in U.S. Pat. No. 4,886,425 is constructed such that an actuating pressure AP of a bypass valve can be controlled by a linear function relation between suction pressure LP and the actuating pressure AP regardless of variations in discharge pressure HP. Hence, the capacity control amount of the compressor can be determined by only the suction pressure LP of the compressor.
On the other hand, the “capacity control device for a compressor” described in Japanese Utility Model Application, First Publication No. Sho 64-56588 is constructed such

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