Pumps – Condition responsive control of drive transmission or pump... – Adjustable cam or linkage
Patent
1996-03-12
1998-11-17
Thorpe, Timothy
Pumps
Condition responsive control of drive transmission or pump...
Adjustable cam or linkage
417269, F04B 129
Patent
active
058367489
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/JP94/01148 filed Jul. 13, 1994.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a swash plate type variable displacement compressor which is used in, for example, an air conditioning system for a vehicle.
2. Description of the Related Art
In general, an electromagnetic clutch is used to connect and disconnect the power transmission path from the engine to a compressor in a refrigerant circuit installed in a car. When an air conditioning system is switched on, the electromagnetic clutch is activated and engine power is transmitted to the compressor via a belt transmission mechanism and the electromagnetic clutch.
Frequent repetition of the connection and disconnection of the electromagnetic clutch to the compressor reduces the durability of the compressor, and also causes the entire refrigerant circuit to instantaneously vibrate when the compressor is activated.
In addition, whenever an electromagnetic clutch is used, the overall size and weight of a compressor is inevitably increased. This requires increased space to mount the compressor in the engine compartment and makes the mounting of the compressor difficult. Further, because the electromagnetic clutch when in action consumes considerable power, the battery in the vehicle must bear a great load.
As a solution to this shortcoming, a clutchless compressor has been proposed whose drive shaft is normally rotated with the engine. While the refrigerant gas is circulating between the compressor and the external refrigerant circuit, therefore, no significant problem arises. When there is an insufficient amount of the gas discharged to the external refrigerant circuit from the compressor, however, the circulation of the gas is stopped, which may cause insufficient lubrication of the sliding portions in the compressor. A clutchless swash plate type compressor designed to overcome this problem is disclosed in Japanese Unexamined Patent Publication No. Hei 3-37378. In this compressor, when the discharge of the gas to the external refrigerant circuit including an evaporator from the compressor is unnecessary, the valve which is connected to the suction chamber is closed to reduce the pressure in the suction chamber and the control valve for the passage between the discharge chamber and the crank chamber is opened.
When the gas discharge is unnecessary, the swash plate of the disclosed compressor is moved to have the minimum inclined angle to minimize the piston stroke. Further, the passage between the external refrigerant circuit and the compressor is blocked to suppress the load with respect to the rotation of the compressor. The slight reciprocation of each piston causes the gas to be discharged to the discharge chamber from the associated cylinder bore and to further flow into the crank chamber via the individual sliding portions from the discharge chamber. The gas in the crank chamber then flows to the suction chamber from which it is drawn into the associated cylinder bore.
According to the conventional compressor, as is apparent from the above, when the discharge of the gas to the external refrigerant circuit from the compressor is unnecessary, a small amount of refrigerant gas is circulated inside the compressor so that oil suspended in the refrigerant gas lubricates the sliding portions. As the gas in the compressor simply circulates, the amount of gas to be circulated is not enough to provide a sufficient amount of lubricating oil, causing insufficient or inadequate lubrication of the individual sliding portions, particularly, in the crank chamber.
Under low temperature conditions as in the winter or the like, when the compressor is stopped during large displacement operation, a large amount of gas remains, liquefied in the crank chamber. With this liquid refrigerant present, even when the compressor is activated, it is difficult to turn the liquid refrigerant to the gaseous state merely by the gas circulation in the compressor which is running now with a small displacement. When t
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Kanzaki Shigeki
Kawaguchi Masahiro
Sonobe Masanori
Suitou Ken
Yokono Tomohiko
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
Kim Ted
Thorpe Timothy
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