Cold accumulation type refrigerating machine

A cold accumulation type refrigerating machine, comprising:

• electric motor means having a rotatable output shaft;
• means for converting a rotation of said output shaft into a linear reciprocative motion of a displacement member disposed within a stationary cylinder;
• a hermetically closed gas expansion chamber defined within said cylinder and having a volume variable as said displacement member moves reciprocatively;
• a gas compressor having an outlet port communicated to said closed chamber through a first valve and a cold accumulator for feeding a compressed gas discharged from said gas compressor to said closed chamber through said cold accumulator when said first valve is opened, said gas being caused to expand within said closed chamber, a second valve being provided in communication with said closed chamber so that said gas which has undergone the expansion within said closed chamber is fed back to said gas compressor through said cold accumulator when said second valve is opened, wherein feed of said compressed gas to said closed chamber, expansion thereof within said closed chamber and feeding back of said gas to said compressor after expansion constitute one cycle of operation of said refrigerating machine;
• temperature sensor means for detecting a temperature of a heat conducting portion provided at a bottom of said cylinder;
• and
• control means for changing a rotation speed of said electric motor means during said one cycle of operation in dependence on a temperature level of said heat conducting portion detected by said temperature sensor means;
• wherein:
• said control means controls the rotation speed of said motor such that said rotation speed of said motor is low during a period extending from a time point at which said second valve is opened to a time point at which said displacement member reaches a top dead center while increasing said rotation speed during the remaining period of said operation cycle, when an output of said temperature sensor indicates a relative high temperature, while when the output of said temperature sensor indicates a relatively low temperature, said control means controls the rotation speed of said electric motor means such that said displacement member moves linearly at a uniform speed from a top dead center thereof to a bottom dead center and from the bottom dead center to the top dead center.

A cold accumulation type refrigerating machine, comprising:

• first electric motor means having a rotatable output shaft;
• first means for converting a rotation of said output shaft into a linear reciprocative motion of a first displacement member disposed within a first stationary cylinder;
• a first gas expansion chamber defined within said first cylinder below said first displacement member and having a volume variable as said first displacement member moves reciprocatively;
• a first cold accumulator disposed externally of said first cylinder in fluid communication with a top chamber defined above said displacement member and said first gas expansion chamber;
• second electric motor means having a rotatable output shaft;
• second means for converting the rotation of said output shaft into a linear reciprocative motion of a second displacement member disposed within a second stationary cylinder disposed downstream of said first cylinder and having a greater volume than that of said first cylinder, said second cylinder having a top chamber defined above said second displacement member and communicated to the top chamber of said first cylinder;
• a second gas expansion chamber defined within said second cylinder and having a volume variable as said second displacement member moves reciprocatively;
• a second cold accumulator disposed externally of said second cylinder in fluid communication with said first and second gas expansion chambers;
• a gas compressor having an outlet port communicated to said first and second gas expansion chambers through a first valve and said first and second cold accumulators for feeding a compressed gas discharged from said gas compressor to said first and second gas expansion chambers through said first and second cold accumulators, respectively, when said first valve is opened, said gas being caused to expand within said first and second gas expansion chambers, said gas compressor having a second valve communicated to said first and second gas expansion chambers so that said gas which has undergone the expansion within said closed chamber is fed back to said gas compressor through said first and second cold accumulators when said second valve is opened;
• first and second sensor temperature sensors disposed at bottoms of said first and second cylinders, respectively;
• and
• control means for controlling rotation speeds of said first and second motors in dependence on outputs of said first and second temperature sensors such that said rotation speed of said first motor is low during a period extending from a time point at which said second valve is opened to a time point at which said first displacement member reaches a top dead center while increasing said rotation speed during the remaining period of said operation cycle, while controlling the rotation speed of said second electric motor means such that said second displacement member moves linearly at a uniform speed from a top dead center thereof to a bottom dead center and from the bottom dead center to the top dead center.

A cold accumulation type refrigerating machine, comprising:

• electric motor means having a rotatable output shaft;
• means for converting a rotation of said output shaft into a linear reciprocative motion of a displacement member disposed within a stationary cylinder;
• a hermetically closed gas expansion chamber defined within said cylinder and having a volume variable as said displacement member moves reciprocatively;
• a gas compressor having an outlet port communicated to said gas expansion chamber through a first valve and a cold accumulator for feeding a compressed gas discharged from said gas compressor to said gas expansion chamber by way of said cold accumulator when said first valve is opened, said gas being caused to expand within said closed chamber, a second valve being provided in communication with said closed chamber so that said gas which has undergone the expansion within said gas expansion chamber is fed back to said gas compressor through said cold accumulator when said second valve is opened, wherein feeding of said compressed gas to said closed chamber, expansion thereof within said closed chamber and feeding back of said gas to said compressor after expansion constitute one cycle of operation of said refrigerating machine;
• pressure sensor means for measuring a pressure within said cylinder;
• temperature sensor means for detecting a temperature of a heat conducting portion provided at a bottom end of said cylinder;
• and
• control means for determining arithmetically a rate of the gas flow into said gas expansion chamber on the basis of outputs of said pressure sensor and said temperature sensor to thereby change a rotation speed of said electric motor means during said one cycle of operation so that said gas flow rate remains substantially constant over said one cycle of operation.