LOW PRESSURE CONTAINER TYPE ROLLING PISTON COMPRESSOR

Abstract: A low pressure container type rolling piston compressor comprises a compression element (23), a motor element (22), a rotary shaft (24) with an eccentric portion (24a) driven by the motor element, a cylinder (25) for receiving therein the eccentric portion (24a) of the rotary shaft, a rolling piston (26) having an inner circumference to which the eccentric portion (24a) is fitted and an outer circumference which rolls along the inner wall surface of the cylinder (25), a vane (28) having an end which is in contact with the outer circumference of the rolling piston (26) to divide the inner space of the cylinder into a high pressure chamber (31) and a low pressure chamber (30), a pair of bearing plates (27a, 27b) for closing both open ends of the cylinder (25), a sealing container housing the above-mentioned structural elements and stor­ ing at its lower part a lubricating oil, wherein the pressure in the sealing container (21) is the same as that in the low pressure chamber (30) and wherein an oil supplying passage (37) is formed in either one of the pair of bearing plates (27a, 27b) so as to communicate the low pressure chamber (30) with the inner space of the rolling piston (26).

Description: The present invention relates to a low pressure container type rolling piston compressor having the features of the first part of claim 1 (EP.A-0 154 347). In the compressor known from the mentioned EP-A lubricating oil is supplied through a passage into a space surrounding an end of the rotary shaft and from there in succession lubricates the adjacent bearing, a thrust bearing or end seal and the inner space of the rolling piston. From DE-A-3 135 438 a vane pump is known in which a lubricating oil passage connects the inner space of the rotating cylinder with the low pressure side of the pump. Figure 4 shows a conventional rolling piston type compressor disclosed in, for instance, Japanese Patent Application No. 161299/1988. In Figure 4, a reference numeral 1 designates a sealing container, a numeral 2 designates a cylinder disposed in the sealing container 1, a numeral 3 designates a rotary shaft arranged at the axial center of the cylinder 2 and having an eccentric shaft portion, a numeral 4 designates a frame or a first bearing plate arranged at an end portion of the cylinder, a numeral 5 designates a cylinder head or a second bearing plate arranged at the other end portion of the cylinder, a numeral 6 designates a rotor, or a rolling piston revolving in the cylinder 2 in an eccentric manner, a numeral 7 designates a low pressure chamber defined by the cylinder and the other elements, a numeral 8 designates a high pressure chamber, a numeral 9 designates a vane for dividing the inside of in the cylinder into the low pressure chamber and the high pressure chamber, a numeral 10 designates a discharge muffler, a numeral 11 designates a gear pump for supplying oil, a numeral 12 designates a motor element, and a numeral 13 desigantes a lubricating oil. The operation of the conventional rolling piston compressor will be described. When the rotary shaft 3 is driven by the motor element 12, oil is supplied from the gear pump 11 placed at an end portion of the rotary shaft 3 to the frame 4 of the rotary shaft 3, bearing portions of the cylinder head 5 and the inner circumferential portion of the rotor 6. Since the rotor 6 is rotated eccentrically in the cylinder 2 and the vane 9 is always in press-contact with the rotor 6, the low pressure chamber 7 and the high pressure chamber 8 are formed in the cylinder 2. Gas introduced from the intake pipe (not shown) or the sealing container 1 to the low pressure chamber 7 is compressed, and the compressed gas is discharged through the high pressure chamber 8 to be discharged through a high pressure pipe extending outside the sealing container 1 via the discharge muffler 10 and a discharge pipe (not shown). In the conventional rolling piston compressor having the above-mentioned construction, a sufficient oil supply is obtained to the bearing portions for supporting the rotary shaft 3. In a case of a high pressure container type compressor, oil supply to the low pressure chamber 7 and the high pressure chamber 8 in the cylinder 2 is conducted by supplying oil through gaps between the structural elements and the rotor 6. However, in the low pressure container type compressor, the pressure of the inner space of the rotor 6 is always lower than that of the high pressure chamber 8 and is the substantially same as that of the low pressure chamber 7. Accordingly, oil supply through the gaps between the rotor 6 and the other structural elements can not be substantially obtained. Therefore, sealing function in the compressor is decreased. This causes that leakage of pressurized gas increases, the performance is reduced and there causes temperature rise at the contacting surface between the rotor 6 and the vane 9. It is the problem underlying the present invention to provide a low pressure container type rolling piston compressor provided with an oil supplying means capable of supplying oil to the low pressure chamber in the cylinder in a stable manner. In accordance with the present invention this problem is solved by claim 1. In the drawings: Figure 1 is a longitudinal cross-sectional view partly omitted of an embodiment of the low pressure container type rolling piston compressor according to the present invention; Figure 2 is a cross-sectional view showing another embodiment of the rolling piston compressor according to the present invention; Figure 3 is a cross-sectional view partly omitted taken along a line III-III in Figure 2; and Figure 4 is a longitudinal cross-sectional view partly omitted of a conventional rolling piston compressor. In Figures 1 to 3, a reference numeral 21 designates a sealing container, a numeral 22 designates a motor element and a numeral 23 designates a compressor element. The motor element 22 and the compressor element 23 are arranged side by side in the sealing container 21 placed with the longitudinal axial line being horizontally. The motor element 22 comprises a stator 22a attached to the inner wall of the sealing container 21 and a rotor 22b rotatably fitted inside the stator 22a. A rotary shaft 24 is fitted to and firmly connected to the rotor 22b. The compressor element 23 has a cylinder 25 in which an eccentric portion 24a formed in the rotary shaft 24 is inserted in the cylinder 25. A rolling piston 26 in a form of cylinder is fitted to the outer circumference of the eccentric portion 24a so as to effect an eccentric rotation in the cylinder 25. Both open ends of the cylinder 25 are closed by a pair of bearing plates 27a, 27b which support the rotary shaft 24 in a rotatable manner. The bearing plates 27a, 27b also support both end surfaces of the rolling piston 26. A vane 28 is held in the cylinder 25 so as to be movable in its axial direction and an end of the vane 28 is in press-contact with the outer circumference of the rolling piston 26 by means of a compression spring 29 so that the inner space of the cylinder 25 is divided into a low pressure chamber 30 and a high pressure chamber 31. A discharge muffler 32 is fixed to the outer end surface of the bearing plate 27b arranged at the opposite side of the rotary shaft 24 with respect to the motor element 22. A gear pump 23 for supplying oil by the rotary movement of the rotary shaft 24 is provided in the discharge muffler 32. A lubricating oil 34 is stored at the lower part of the sealing container 21. An oil intake pipe 35 connected to the discharge muffler 32 opens in the lubricating oil 34 and the oil intake pipe 35 is connected to the intake side of the gear pump 33. A numeral 58 designates a recess for oil sump formed in the inner surface of the bearing plate 27a. The recess for oil sump 58 is formed in such a position and in such a size that during one revolution of the rotary shaft 24, three phases are obtained by the eccentric revolution of the rolling piston, namely a phase in which the recess 58 is communicated with the low pressure chamber 30 in the cylinder 25, a phase in which the recess 58 is closed by the end surface of the rolling piston 26, and a phase in which the recess is communicated with the inner space of the rolling piston 26. Recess 58 is formed in the end surface of the bearing plate 27a facing the cylinder 25 at a position near the vane 28 with respect to an inlet 59 formed in the cylinder 25 and has a diameter smaller than the thickness in the radial direction of the rolling piston 26. The operation will be described. When the rotary shaft 24 is driven by the motor element, gas such as a refrigerant gas is introduced for compression in the low pressure chamber 30 in the cylinder 25. The compressed gas is discharged to the high pressure pipe extending to outside the sealing container through the discharge pipe (not shown) and lubricating oil stored at the bottom of the sealing container is supplied to the bearing portions of the compressor element 23 via the oil pipe 56 (which is effected by actuating the gear pump due to the revolution of the rotary shaft 24). The rolling piston 26 rolls along the inner circumferential wall of the cylinder 25 in one revolution of the rotary shaft 24, and the lubricating oil in the inner space of the piston 26 is supplied to the recess 58 in the phase in which the recess 58 is exposed in the inner space of the piston 26. The lubricating oil has been introduced in the inner space of the piston 26 through the oil pipe 56. In the next phase the recess 58 is closed by the end surface of the rolling piston 26, the lubricating oil being kept in the recess 58. When the recess 58 is communicated with the low pressure chamber 30, the lubricating oil in the recess 58 flows into the low pressure chamber 30 by the action of a stream of intake gas, whereby the recess 58 from which the lubricating oil has been discharged is again closed by the rolling piston 26. Then, returning to the original situation, the recess 58 is communicated with the inner space of the rolling piston 26. Accordingly, the lubricating oil can be supplied to the low pressure chamber in an amount in proportion to the volume of the recess 58 regardless of conditions of pressure for each revolution of the rotary shaft 24 in the operation of the compressor, and a stable amount of oil can be supplied. The recess 58 is formed at a position close to the vane 28 with respect to the inlet 59 of the cylinder 5, and accordingly, the lubricating oil can be smoothly supplied to the vane 28, whereby the wear-resistance of the vane 28 can be improved. The recess 58 is formed in the bearing plate 28a at the side of the motor element in the above-mentioned embodiment. However, the recess may be formed in the bearing plate 27b. Or it may be formed in the both bearing plates 27a, 27b. Any type of pump may be used for the gear pump which supplies the lubricating oil. Thus, in accordance with the above-mentioned embodiment of the present invention, a constant amount of the lubricating oil can be supplied in proportion to the volume of the recess to the low pressure chamber regardless of condition of pressure, for each revolution of the rotary shaft. Accordingly, the escaping of lubricating oil at the time of starting can be controlled, and lack of lubricating oil can be eliminated. Further, when the rolling piston compressor is used for a refrigeration cycle, reduction of heat exchanging efficiency in a heat exchanger is avoidable.

Claims: A low pressure container type rolling piston compressor comprising a compression element (23), a motor element (22), a rotary shaft (24) with an eccentric portion (24a) driven by said motor element (22), a cylinder (25) for receiving therein said eccentric portion (24a) of the rotary shaft, a rolling piston (26) having an inner circumference to which said eccentric portion (24a) is fitted and an outer circumference which rolls along the inner wall surface of said cylinder (25), a vane (28) having an end which is in contact with the outer circumference of said rolling piston (26) to divide the inner space of said cylinder (25) into a high pressure chamber (31) and a low pressure chamber (30), a pair of bearing plates (27a, 27b) for closing both open ends of said cylinder, a sealing container (21) housing the above-mentioned structural elements and storing at its lower part a lubricating oil wherein a pressure in said sealing container (21) is the same as that in said low pressure chamber (30), wherein an oil supplying passage (58) in one of said bearing plates (27a, 27b) communicates said low pressure chamber (30) with the inner space of the rolling piston (26), characterized in that said oil supplying passage is formed by a recess (58) in the inner surface of at least one of said pair of bearing plates (27a, 27b), that the position and the size of said recess are dimensioned such that during one revolution of said rotary shaft (24) three phases are obtained, wherein the recess (58) is communicated with said low pressure chamber (30) in said cylinder (25) in a first phase, the recess (58) is closed by the end surface of said rolling piston (26) in a second phase, and the recess (58) is communicated with the inner space of said rolling piston (26) in a third phase by the eccentric revolution of said rolling piston (26). The compressor according to claim 1, characterized in that said recess (58) is formed in the end surface of the bearing plate (27a) facing said cylinder (25) at a position near said vane (28) with respect to an inlet formed in said cylinder and has a diameter smaller than the thickness of said rolling piston (26) in radial direction.

Inventors: KAWAGUCHI, SUSUMU MITSUBISHI DENKI K.K., MAEYAMA, HIDEAKI MITSUBISHI DENKI K.K., SHIRAFUJI, YOSHINORI MITSUBISHI DENKI K.K., SUGITA, TATSUYA MITSUBISHI DENKI K.K., YAMAMOTO, TAKASHI MITSUBISHI DENKI K.K.
Applicants: MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1989
Main classification: F04C29
IPC codes: F04C29