Pumps – Condition responsive control of drive transmission or pump... – Adjustable cam or linkage
Reexamination Certificate
2000-12-07
2002-11-19
Freay, Charles G. (Department: 3746)
Pumps
Condition responsive control of drive transmission or pump...
Adjustable cam or linkage
C417S199100, C417S222100, C417S269000, C417S295000, C137S454600, C251S061500
Reexamination Certificate
active
06481976
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a control valve, used for a variable capacity type compressor constituting a refrigerant circulating circuit of a vehicle air conditioner to compress refrigerant gas and also to a variable capacity compressor having such a control valve.
2. Description of the Related Art
As this type of variable capacity compressor, for example, a swash plate type variable capacity type compressor is known and is shown in FIG.
9
. In the variable capacity type compressor, which will be simply referred to as a compressor in this specification hereinafter, when the swash plate
101
is rotated, the pistons
102
are reciprocated, so that refrigerant gas is compressed, and the discharge capacity can be adjusted when the pressure in the crank chamber
103
is adjusted. In this case, the swash plate
101
is driven by an engine of a vehicle, which is an external drive source.
In order to adjust the pressure in the crank chamber
103
, there are provided an extraction gas passage
105
having a fixed restriction
105
a
connecting the crank chamber
103
to the suction chamber
104
, a supply passage
107
connecting the discharge chamber
106
to the crank chamber
103
, and an electromagnetic control valve
108
arranged in the supply passage
107
. When the degree of opening of the control valve
108
is adjusted, the quantity of high pressure gas supplied from the discharge chamber
106
into the crank chamber
103
via the supply passage
107
is controlled with respect to the quantity of gas extracted from the crank chamber
103
into the suction chamber
104
via the extraction passage
105
, so that the pressure in the crank chamber
103
can be determined. According to the change in the pressure in the crank chamber
103
, a difference between the pressure in the crank chamber
103
and the pressure in the cylinder bores
109
on either side of the piston
102
is changed, so that the inclination angle of the swash plate
101
can be changed. According to the change in the inclination angle of the swash plate
101
, the stroke of the pistons
102
is adjusted, that is, the discharge capacity of the compressor can be adjusted.
For example, when the pressure in the crank chamber
103
is raised and a difference between the pressure in the crank chamber
103
and the pressure in the cylinder bores
109
is increased, the inclination angle of the swash plate
101
is decreased, so that the discharge capacity of the compressor is decreased. In the drawing, the swash plate
101
shown by a solid line is located at the minimum inclination angle. On the contrary, when the pressure in the crank chamber
103
is lowered and a difference of between the pressure in the crank chamber
103
and the pressure in the cylinder bores
109
is decreased, the inclination angle of the swash plate
101
is increased, so that the discharge capacity of the compressor is increased. In the drawing, the swash plate
101
shown by a two-dotted chain line is located at the maximum inclination angle.
However, a problem may arise in that, when the air conditioner having the compressor of the above structure, for example, is started at midday or in the afternoon in summer, substantially simultaneously with the start of a vehicle engine, the air conditioning operation should be started immediately according to the demand of an operator, but there is a case in which it takes several tens of seconds to actually start the effective air conditioning operation. The reason why it takes several ten seconds to start the effective air conditioning operation is that the change of the operating condition of the compressor from the minimum discharge capacity state is delayed and it takes time for the compressor to reach the maximum discharge capacity state. The reason why the change of the operating condition from of the compressor the minimum discharge capacity state is delayed is that a large quantity of liquid refrigerant, which stays in the crank chamber
103
during the stoppage of the engine, is agitated and evaporated by the heat generated at the start of the compressor and the rotation of the swash plate
101
, and therefore, refrigerant gas cannot be sufficiently extracted from the crank chamber
103
in a short period of time, and the pressure in the crank chamber
103
is kept high. That is, the swash plate
101
is held at the minimum inclination angle irrespective of the adjustment of the degree of opening of the supply passage
107
conducted by the control valve
108
until evaporation of liquid refrigerant in the crank chamber
103
is completed.
The reason why a large quantity of liquid refrigerant stays in the crank chamber
103
during the stoppage of the engine as described above is because of a difference between the thermal capacity of the compressor and that of the condenser
111
or the evaporator
112
in the external refrigerant circuit. That is, the condenser
111
and the evaporator
112
, which are heat exchangers, are easily influenced by the change in the temperature in the surroundings, but, the compressor, the thermal capacity of which is large and the surface area of which is small, is less influenced by the change in the temperature in the surroundings. Accordingly, as the temperature of the outside air rises from the morning to the noon, the temperature of the condenser
111
and the evaporator
112
, which are easily influenced by the temperature change, is quickly raised and the temperature of the compressor, which is less influenced by the temperature change, is slowly raised, so condensation of refrigerant gas begins in the compressor due to the difference between the temperature of the condenser
111
and the evaporator
112
and the temperature of the compressor. When condensation of refrigerant gas begins in the compressor, the volume of refrigerant is reduced due to the transfer from the gaseous state to the liquid state, and the pressure in the compressor is reduced, so that a flow of refrigerant gas directly from the condenser
111
and the evaporator
112
into the compressor occurs. Refrigerant gas flowing from the condenser
111
and the evaporator
112
into the compressor is condensed and the flow of refrigerant gas into the compressor and the condensation of refrigerant gas in the compressor are repeated. At midday or in the afternoon when the rise of temperature of the outside air is substantially settled and the difference between the temperature of the compressor and the temperature of the condenser
111
and the evaporator
112
becomes smaller, the quantity of liquid refrigerant in the compressor (crank chamber
103
) becomes a maximum.
In order to solve the above problems, the following three countermeasures can be considered.
The first countermeasure is that the minimum inclination angle of the swash plate
101
is set to a greater value. By doing so, even if the compressor is in the minimum discharge capacity state, a certain flow rate of refrigerant can be ensured in the refrigerant circulating circuit. Accordingly, even if the change of the operating condition of the compressor from the minimum discharge capacity state is hindered when liquid refrigerant is in the crank chamber
103
as described above, the compressor can suck and discharge a certain amount of refrigerant, so the suction pressure is quickly lowered and refrigerant is quickly extracted from the crank chamber
103
, and the operating condition of the compressor can be changed from the minimum discharge capacity state in a short period of time. However, when an absolute value of the minimum discharge capacity is made higher, the compressor can not cope with a state in which the load of air conditioning is low, and in the case where a power transmission mechanism having a clutch between the compressor and the vehicle engine is adopted, it becomes necessary to turn the clutch on and off frequently.
Also, in the case where a clutchless type power transmission mechanism is adopted, the compressor is driven at all times while th
Fukanuma Tetsuhiko
Kawaguchi Masahiro
Kayukawa Hiroaki
Kimura Kazuya
Freay Charles G.
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
Woodcock & Washburn LLP
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