Rotary compressor, heat pump, and household appliance

Abstract

A rotary compressor includes a cylindrical housing, a cylindrical roller accommodated in the housing, a motor shaft leading through the roller having a cam for rolling the roller along a side wall of the housing, and a discharge port leading through a bottom cover, wherein a height-to-radius ratio of the roller is between 6 and 1.2, a radius of the motor shaft is 8.0 mm or less, a cam height of 14 mm or less, an area of the discharge port of 17 mm.sup.2 or more, and a thickness of the discharge port of 2.5 mm or less. For operation of the compressor, a top cover may be put onto the top open side of the housing. The top cover may have a bushing for the shaft. A heat pump includes the compressor. A household appliance, in particular laundry care apparatus, includes the heat pump.

Claims

1. A rotary compressor, comprising a cylindrical housing having a first longitudinal axis, a cylindrical roller having a second longitudinal axis and being accommodated in the housing such that the second longitudinal axis is aligned parallel and spaced apart from the first longitudinal axis, a rotatable motor shaft leading through the roller having a cam for rolling the roller along a side wall of the housing, and a discharge port leading through a bottom cover, wherein a height-to-radius ratio of the roller is between 1.6 and 1.2, a radius of the motor shaft is no more than 8 mm, a height of the cam is no more than 14 mm, an effective area of the discharge port is at least 17 mm.sup.2, and a thickness of the discharge port is no more than 2.5 mm.

2. The rotary compressor according to claim 1, wherein a displacement of the compressor is between 6 cc and 9.5 cc.

3. The rotary compressor according to claim 2, wherein the displacement is in the range from 7.9 cc to 8.3 cc.

4. The rotary compressor according to claim 1, wherein the height of the cam is 12.8 mm or less.

5. The rotary compressor according to claim 1, comprising an oil selected from the group having a PAG type oil having a kinematic viscosity between 95 cSt at 40 C. and 105 cSt at 40 C., and a POE type oil having a kinematic viscosity between 60 cSt at 40 C. and 105 cSt at 40 C.

6. The rotary compressor according to claim 5, wherein an oil quantity of the oil in the compressor is between 150 cc and 210 cc.

7. The rotary compressor according to claim 1, wherein the rotary compressor is provided for use as a part of a heat pump.

8. A heat pump for a household appliance, comprising a compressor, a condenser, a restrictor, and an evaporator, wherein the compressor is a rotary compressor according to claim 1.

9. The heat pump according to claim 8, wherein a refrigerant used with the heat pump is a flammable refrigerant having a charge of 150 g or less.

10. The heat pump according to claim 9, wherein R290 is used as the refrigerant.

11. The heat pump according to claim 8, wherein R407C or R134a is used as the refrigerant.

12. A household appliance for a laundry care apparatus, comprising a heat pump, wherein the heat pump is a heat pump according to claim 8.

13. The household appliance according to claim 12 wherein the household appliance is the laundry care apparatus that comprises a tumble dryer function.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the figures of the attached drawing, the invention is highlighted by means of an exemplary embodiment schematically shown, and will be explained further subsequently with reference to that exemplary embodiment. In particular,

(2) FIG. 1 shows a schematic drawing of a household tumble dryer using a heat pump;

(3) FIG. 2 shows a top view onto an opened rotary compressor; and

(4) FIG. 3 shows a cross-sectional side view of the opened rotary compressor of FIG. 2.

DETAILED DESCRIPTION

(5) FIG. 1 shows a clothes treatment appliance in form of a household tumble dryer H. The tumble dryer H comprises a heat pump P having at least a compressor 1, a condenser 2 (e.g. of a tube-and-fins type), a restrictor 3 (e.g. a valve), and an evaporator 4 (e.g. of a tube-and-fins type) as elements. The elements 1 to 4 are serially connected in the shown order by refrigerant pipes 5 to form a refrigerant circuit or path.

(6) The tumble dryer H also comprises a process air circuit or path 6 wherein process air A flows. The air circuit 6 comprises a rotatable drum 7 for holding to be processed clothes. The air A leaves the drum 7 at a medium temperature and wet. The air A then flows to the evaporator 4 that is placed in the air circuit 6 downstream the drum 7 and works as a heat exchanger. At the evaporator 4, the air A is cooled down and condenses. The resultant condensate is collected in a water tank W. At the evaporator 4, the air A also cools down and transfers part of its thermal energy upon the evaporator 4 and thus onto the refrigerant R within the evaporator 4. This enables the evaporator 4 to transform the refrigerant R from a liquid state into a vaporous state.

(7) Further downstream the air circuit 6 the now dry and cool air A passes through the condenser 2 where a heat transfer from the condenser 2 and the refrigerant R, resp., to the air A is effected to heat up the air A and cool down the refrigerant R to its liquid state. The then warm and dehumidified/dry air A is subsequently reintroduced into the drum 7 to warm up the clothes and to pick up moisture. The refrigerant R is moved within the refrigerant circuit 1 to 5 by the compressor 1. The refrigerant R is a flammable refrigerant, in particularly R290. An amount of the flammable refrigerant R is 150 g or less.

(8) The evaporator 4 and the condenser 2 are thus used as heat exchangers.

(9) The working of such a tumble dryer H with its heat pump P (comprising the refrigerant circuit 1 to 5) and its air circuit 6 is well known and does not need to be explained in greater detail.

(10) FIG. 2 shows a top view onto an opened rotary compressor 1 of the household tumble dryer H. FIG. 3 shows a cross-sectional side view of the opened rotary compressor of FIG. 2.

(11) The compressor 1 comprises a hollow cylindrical housing 8 with a cavity 9 which houses a hollow cylindrical roller 10. A lower end face 1 1 of the roller 10 is supported by a bottom cover 12. The lower end face 1 1 of the roller 10 can move or slip along an inner side of the bottom cover 12. A longitudinal axis L1 of the housing 8 and a longitudinal axis L2 of the roller 10 are aligned in parallel but spaced apart. The roller 10 is rollingly rotated within the housing 8 by a shaft 13 that is connected to an electrical motor (not shown). The shaft 13 lies concentric to the housing 8 and is thus eccentric to the roller 10. To be able to rotate the roller 10 within the housing 8, the shaft 13 has a laterally positioned cam 14 or cam portion (only shown in FIG. 3) that presses the roller 10 onto an inner face of a side wall 15 of the housing 8. The roller 10 thus has a contact line K with the side wall 15. When the shaft 13 rotates it rolls the roller 10 along the side wall 15.

(12) A path of the contact line K at the inner side wall 15 then describes a closed loop. A displacement of the compressor 1 for one full rotation of the roller 10 is between 6 cc and 9.5 cc, in particular in the range of 7.9 cc to 8.3 cc, in particular 8.1 cc. A length of the contact line K corresponds to a height hr of the roller 10 at the side wall 15.

(13) The shaft 13 is formed as a hollow cylinder such that is can be connected to an oil pump (not shown) to feed oil into the compressor 1. The oil quantity within the compressor 1 is between 150 cc and 210 cc, preferably 180 cc or less. The oil may in particular be PAG PZ100S, POE RB-P68EP, or POE RP-100EP, or an equivalent.

(14) Into the cavity 9 of the housing 8 protrudes a blade 16 that contacts an outer side face of the roller 10. The housing 8 also has a suction port 17 leading through its wall to suck refrigerant R into the cavity 9 and a discharge port 18 leading through the bottom cover 12 to discharge the refrigerant R. The side wall 15 of the housing 8 has a recessed section 20 adjacent to and above the discharge port 18 to avoid covering the discharge port 18. A cross-sectional area Q of the discharge port 18 is 23 mm.sup.2 or more, preferably larger than 28 mm.sup.2, preferably 34 mm.sup.2 or larger. A thickness d of the discharge port 18 (corresponding to its height along the longitudinal axis L1) is 2.5 mm or less.

(15) For operation of the compressor, a cover lid or top cover 19 (shown as a dashed line) is put onto the open side of the housing 8. The top cover 19 may have a bushing for the shaft 13.

(16) In FIG. 3, a ratio hr/rr of a height hr to a radius rr of the roller 10 (the height-to-radius ratio hr/rr) is between 1.6 and 1.2, preferably less than 1.6.

(17) A radius rs of the shaft 13 (without the cam 14) is 8.0 mm or less.

(18) The internal elements 8, 10 to 14, 16, and 19 of the compressor 1 are moving at different rotation speeds during operation of the compressor 1. This difference in the speed produces friction between these elements 8, 10 to 14, 16, and 19.

(19) The friction losses associated with such friction are produced by two kinds of lubrication (i) hydrodynamic lubrication and (ii) boundary lubrication. With hydrodynamic lubrication, a full film of oil exists between moving contact surfaces. For hydrodynamic lubrication, the friction forces can be calculated considering oil as a Newtonian fluid, i.e. using F=.Math.A.Math.u/y, wherein F is a force required to move two parallel surfaces of area A that are separated be a distance y with a constant speed u. represents the dynamic viscosity of the oil between the surfaces (contact surfaces or friction surfaces). With boundary lubrication, a thin film of oil is located between moving surfaces. In this case, a direct contact between surfaces is produced. For calculating the respective friction force F, a well-known linear friction law according to F=.Math.N with being a friction coefficient and N being a normal force can be used. Calculation for the compressor 1 confirmed that the compressor 1 has significantly lower friction losses, especially because of a reduction of the friction between the roller 10 and the cam 14 and between the motor shaft 13 and the bottom wall 12 of the housing 8. This is caused by smaller friction areas as well as lower linear velocities between the friction surfaces of the compressor 1.

(20) Of course, the invention is not restricted to the embodiments shown.

LIST OF REFERENCE NUMERALS

(21) 1 compressor 2 condenser 3 restrictor 4 evaporator 5 refrigerant pipe 6 air circuit 7 rotatable drum 8 housing 9 cavity 10 roller 11 lower end face of the roller 12 bottom wall of bottom cover 13 shaft 14 cam 15 side wall of the housing 16 blade 17 suction port 18 discharge port 19 top cover 20 recessed section of the housing A air d thickness of the discharge port H tumble dryer hc height of the cam hr height of the roller K contact line L1 longitudinal axis L1 of the housing L2 longitudinal axis L2 of the roller P heat pump Q area of the discharge port R refrigerant rr radius of the roller rs radius of the shaft W water tank