Patent ID: 7207191

Claim:
A cryogenic refrigerator comprising: a discharging port for pressure-feeding a refrigerant; a suction port for sucking the refrigerant; a pressure feeding means including the discharging port and the suction port; a refrigeration means for refrigerating a body to be refrigerated; a high pressure passage for establishing communication between the discharging port of the pressure feeding means and the refrigeration means, the high pressure passage being introduced with the refrigerant with relatively high pressure; a low pressure passage for establishing the communication between the suction port of the pressure feeding means and the refrigeration means, the low pressure passage being introduced with the refrigerant with relatively low pressure; and at least one heat exchanger at the high pressure passage for refrigerating the refrigerant introduced at the high pressure passage by heat exchange, the heat exchanger including an active pressure drop type heat exchanger for declining pressure of the refrigerant at the high pressure passage before being introduced into the refrigeration means, wherein the active pressure drop type heat exchanger declines the pressure of the refrigerant with a ratio equal to or greater than 5 percent out of 100 percent and refrigerates the refrigerant when a pressure difference between a pressure of the refrigerant before being introduced into the active pressure drop type heat exchanger and a pressure of the refrigerant before being introduced into the refrigeration means is defined as 100 percent, and wherein the active pressure drop type heat exchanger declines the pressure of the refrigerant with a ratio equal to or greater than 50 percent out of 100 percent when the pressure difference between the pressure of the refrigerant before being introduced into the active pressure drop type heat exchanger and the pressure of the refrigerant before being introduced into the refrigeration means is defined as 100 percent.