ELECTRIC SCROLL COMPRESSOR

Description

[0001] The invention relates to an electric scroll compressor with a compressor housing having a compressor inlet and a compressor outlet, a compressor unit having a driven eccentric unit, a fixed scroll and a displacement scroll arranged on the eccentric unit, orbiting and engaging in the fixed scroll, an electric motor having a fixed stator and a rotating rotor, wherein the eccentric unit is fastened to the rotor, and wherein at least one balancing weight is arranged on the rotor, and a high-pressure chamber which is fluidly arranged between the compressor outlet and the compressor unit.

[0002] Such electric scroll compressors are well known from the prior art, for example from DE 10 2018 110 025 B4, and comprise a compressor housing, a compressor unit, and an electric motor. The compressor unit and the electric motor are arranged in the compressor housing. The compressor housing has a compressor inlet and a compressor outlet, with a fluid flowing through the compressor inlet into a low-pressure chamber, flowing through the compressor unit, and finally flowing out of the compressor via the compressor outlet from a high-pressure chamber. The compressor unit comprises an orbiting displacement scroll and a fixed scroll that interacts with the displacement scroll and is attached to the compressor housing.The displacement spiral is driven by an electric motor, which has a stator attached to the compressor housing and a rotor rotatably mounted on the compressor housing via two bearing elements. The rotor drives the displacement spiral via an eccentric unit, resulting in the orbiting motion of the displacement spiral.

[0003] During operation of the scroll compressor, the masses to be moved, and in particular the gas forces that vary depending on the operating point, cause a dynamic imbalance of the rotor, resulting in vibrations, unwanted noise, and increased loads on the bearing elements that support the rotor's rotation. Such dynamic imbalances arise because the axis of rotation does not align with one of the component's principal axes of inertia, but is tilted relative to the principal axes of inertia at the center of gravity. This creates bending moments, known as imbalance moments, on the axis of rotation. These cause circular vibrations shifted by 180 degrees at the ends of the rotating body, thus causing the body to wobble.

[0004] To reduce such dynamic imbalance, the electric motor has a balancing weight on each of its end faces. A scroll compressor with a balancing weight is disclosed, for example, in US Pat. Nos. 6,305,914 B1 and 6,123,527 A.

[0005] Typically, the balancing weights are designed and positioned to compensate for dynamic imbalance. The balancing weights can be dimensioned and positioned to compensate exclusively for the dynamic imbalance caused by the moving masses. Alternatively, the balancing weights can be designed and positioned to additionally compensate for the dynamic imbalance caused by gas forces. The dynamic imbalance is compensated as best as possible at a predefined operating point, i.e., at a predefined suction pressure (pressure at the compressor inlet) and a predefined high pressure (pressure at the compressor outlet).The problem is that the dynamic imbalance compensation only applies to the predefined operating point, while at other operating points of the scroll compressor, the balancing weight has a significantly reduced effect on compensating the dynamic imbalance or even increases the dynamic imbalance. The electric scroll compressor is typically operated at different operating points, i.e., with different suction and / or discharge pressures. As a result, at operating points deviating from the predefined operating point, the balancing weights cannot exert the same effect on vibrations, unwanted noise, and loads on the bearing elements as at the design point, i.e., the predefined operating point, and / or may even increase the dynamic imbalance.

[0006] The task therefore arises to further develop an electric scroll compressor in such a way that the electric scroll compressor has reduced vibration and noise development and reduced load on the bearing elements supporting the rotor during operation at different operating points.

[0007] This object is achieved by a scroll compressor having the features of main claim 1.

[0008] Because the balancing weight is arranged radially displaceably on the rotor, and the rotor has a rotor pressure chamber that is at least radially delimited by the balancing weight and fluidly connected to the high-pressure chamber, the balancing weight being radially positionable depending on the pressure prevailing in the rotor pressure chamber, the dynamic imbalance is compensated for depending on the temporarily existing operating point. This allows, in particular, the portion of the dynamic imbalance caused by the gas forces occurring during the compression process and dependent on the operating point to be compensated.

[0009] Depending on the operating point of the electric scroll compressor, the high pressure and suction pressure vary, which in turn varies the load on the compressor unit and rotor caused by the high pressure and suction pressure. This variation in load typically results in a tilting of the rotor's principal axis of inertia relative to the rotational axis defined by the bearing elements, depending on the operating point. This results in a dynamic imbalance that is dependent on the operating point. Because the radial position of the balancing weight depends on the high pressure and thus on the operating point, the tilting of the rotor's principal axis of inertia relative to the rotational axis is counteracted at all operating points. This reduces the dynamic imbalance for each individual operating point.

[0010] Preferably, a backpressure chamber is provided adjacent to the displacement scroll, which is fluidly connected to the high-pressure chamber via a gas connection channel, with the rotor pressure chamber being fluidly connected to the high-pressure chamber via the backpressure chamber. The backpressure chamber is defined by the compressor housing and the displacement scroll and serves to seal the two scrolls. The pressure prevailing in the backpressure chamber and acting on the displacement scroll generates a resulting force in the axial direction, which presses the displacement scroll axially against the stationary scroll.

[0011] The back pressure chamber is directly adjacent to the rotor, i.e. it is arranged on the side of the compressor unit facing the electric motor, so that a fluidic connection between the rotor pressure chamber and the back pressure chamber can be realized in a simple manner and by minor modifications of the spiral casing.

[0012] Preferably, the rotor pressure chamber is fluidly connected to the backpressure chamber via a gas guide channel, wherein the gas guide channel is formed in the rotor. The backpressure chamber is arranged on the axial side of the displacement spiral facing away from the stationary spiral and is directly adjacent to the rotor. By connecting the rotor pressure chamber to the backpressure chamber, the rotor pressure chamber can be supplied with the pressurized gas simply and cost-effectively through a single gas guide channel formed on the rotor, for example, on a rotor shaft.

[0013] Preferably, the balancing weight is located on an axial end face of the rotor. This allows the balancing weight to be easily mounted on the rotor.

[0014] In a preferred embodiment, the balancing weight is arranged in a radial home position by means of a preloaded spring element and, depending on the pressure prevailing in the rotor base chamber, in at least one radial pressure position. The spring element is designed such that the balancing weight is held in a predefined radial home position, with the balancing weight being pressed against a stop, for example, by the spring element. In this radial home position, the balancing weight serves to compensate for the dynamic imbalance at a predefined operating point, for example, the operating point with the lowest initial or high pressure.At other operating points, a pressure prevailing in the rotor pressure chamber, which either depends on the high pressure or corresponds to the high pressure, leads to a radial displacement of the balancing weight. This radial displacement of the balancing weight compensates for the dynamic imbalance caused by the high pressure. This balances the rotor at different operating points.

[0015] In a preferred embodiment, a rotor pressure chamber element is provided with a base, a cover, and several side walls, which is arranged on an axial end face of the rotor, wherein the balancing weight is guided radially through the side walls. The rotor pressure chamber element, with the cover and the side walls, partially delimits the rotor pressure chamber. The balancing weight is arranged within an interior space of the rotor pressure chamber element and also delimits the rotor pressure chamber and rests fluid-tight against the side walls. As a result, a radial force acts on the balancing weight, which results from the pressure prevailing in the rotor pressure chamber and the effective area. The separate rotor pressure chamber element, which can be mounted on an end face of the rotor, can be mounted on the rotor easily and inexpensively.

[0016] Preferably, the spring element is a compression spring arranged between the balancing weight and the floor, or a tension spring arranged between the ceiling and the balancing weight, such that the balancing weight is loaded radially inward by the compression spring or the tension spring. This allows the balancing weight to be held in its radial home position by a simple and cost-effective spring element.

[0017] Preferably, a first balancing weight and a second balancing weight are provided, wherein a first balancing weight is arranged on a first axial end face of the rotor and a second balancing weight is arranged on a second axial end face opposite the first end face. Both balancing weights are arranged radially displaceably on the rotor, each adjacent to a rotor pressure chamber, and are radially positionable depending on the pressure prevailing in the respective rotor pressure chamber. This allows the dynamic imbalance to be reliably reduced.

[0018] This creates an electric scroll compressor which, at different operating points, exhibits reduced vibration and noise development and reduced stress on the bearing elements supporting the rotor.

[0019] An embodiment of an electric scroll compressor according to the invention is shown in the figure and described below.

[0020] The figure shows a sectional view of a scroll compressor according to the invention.

[0021] The scroll compressor 2 comprises a compressor housing 10, which defines a motor chamber 18 and a compressor chamber 20.

[0022] An electric motor 22 with a stator 24 and a rotor 26 is arranged in the motor compartment 18. The rotor 26 is fastened to a rotor shaft 28. The rotor shaft 28 extends from the motor compartment 18 through a central opening 29 into the compressor compartment 20. The rotor shaft 28 is mounted in two shaft bearings 40, 42 via two end-side shaft bearing sections 30, 34, rotatably about a rotor shaft rotation axis. On the side of the second shaft bearing 42 facing the motor compartment 18, a shaft sealing ring 43 is provided, which rests against the rotor shaft 28 with its radial inner side and is supported by the compressor housing 10 with its radial outer side. The shaft sealing ring 43 fluidically seals the motor compartment 18 against a backpressure chamber 69 of the compressor compartment 20.

[0023] A compressor unit 58 is arranged in the compressor chamber 20, which has an orbiting displacement spiral 60 and a stationary spiral 62. The orbiting displacement spiral 60 is arranged on an eccentric unit 50 fastened to the rotor shaft 28 via an eccentric shaft bearing 64 and rests on a surface of the compressor housing 10 facing the compressor chamber 20 via a sliding disk 71. The stationary spiral 62 is fixedly arranged in the compressor housing 10.

[0024] During operation of the scroll compressor 2, a refrigerant is introduced through a compressor inlet 4 into the motor chamber 18 of the scroll compressor 2, whereby the refrigerant flows through the motor chamber 18 into the compressor chamber 20. Rotation of the rotor shaft 28 and thus of the eccentric 50 about the rotor rotation axis generates an orbiting movement of the displacement spiral 60. The orbiting displacement spiral 60 and the fixed spiral 62 are designed such that they delimit a compression chamber 63, and the orbiting movement of the displacement spiral 60 conveys a refrigerant from a radially outer inlet 66 of the compression chamber 63 to a radially inner outlet 67 of the compression chamber 63, where it is compressed.

[0025] The compressor chamber 20 has a high-pressure chamber 68 and a backpressure chamber 69. The high-pressure chamber 68 is defined by the compressor housing 10 and the stationary scroll 62 and is fluidly arranged between the outlet 67 and a compressor outlet 6, with the refrigerant flowing from the outlet 67 via the high-pressure chamber 68 to the compressor outlet 6. From the compressor outlet 6, the refrigerant flows into a coolant circuit of a motor vehicle.

[0026] The backpressure chamber 69 is defined by the compressor housing 10 and the orbiting displacement scroll 60. The backpressure chamber 69 is fluidly connected to the high-pressure chamber 68 via a gas connection channel 70. The gas connection channel 70 extends from the high-pressure chamber 68 through the stationary scroll 62 and through the compressor housing 10.

[0027] The pressure prevailing in the backpressure chamber 69 acts on the axially displaceable, orbiting displacement scroll 60, resulting in an axial load on the displacement scroll 60. This axial load leads to an improved seal between the end faces of the orbiting displacement scroll 60 and the stationary scroll 62.

[0028] During operation of the scroll compressor, the masses to be moved, and in particular the gas forces that vary depending on the operating point, cause a dynamic imbalance of the rotor 26, resulting in vibrations, undesirable noise, and increased loads on the shaft bearings 40, 42 that rotatably support the rotor 26. To reduce such dynamic imbalance, the rotor 26 has a radially displaceable balancing weight 72, 74 and a rotor pressure chamber element 76, 78 at each of its axial ends.

[0029] The rotor pressure chamber elements 76, 78 each have a plurality of side walls, a floor and a ceiling, and each delimit a space 80, 82. The balancing weight 72, 74 is arranged inside the space 80, 82, and is guided by the side walls of the rotor pressure chamber elements 76, 78 such that the balancing weights 72, 74 are radially movable. The balancing weights 72, 74 are each loaded in the radial direction, i.e. radially inward, by a spring element 84, 86, which is designed as a compression spring and is arranged between the ceiling of the rotor pressure chamber elements 76, 78 and the balancing weights 72, 74.

[0030] On the side of the balancing weights 72, 74 opposite the spring element 84, 86, a rotor pressure chamber 88, 90 is provided. The rotor pressure chambers 88, 90 are each delimited by the balancing weight 72, 74, the side walls of the rotor pressure chamber element 76, 78, and the bottom of the rotor pressure chamber element 76, 78. The rotor pressure chambers 88, 90 are fluidly connected to the counterpressure chamber 69 via a gas guide channel 92, so that a pressure dependent on the pressure of the counterpressure chamber 69 prevails in the rotor pressure chambers 88, 90. The pressure prevailing in the rotor pressure chambers 88, 90 loads the balancing weights 72, 74 radially and against the spring force of the spring elements 84, 86. As a result, the balancing weights 72, 74 are displaced radially depending on the pressure prevailing in the rotor pressure chambers 88, 90 and thus on the operating pressure of the scroll compressor 2.

[0031] The radially moving balancing weights 72, 74 compensate for the dynamic imbalance depending on the temporarily prevailing operating point, i.e., the pressure prevailing in the high-pressure chamber 68. At a predefined operating point, the balancing weight 72, 74 is loaded into a radial home position by the spring element 84, 86, whereby the balancing weights 72, 74 are pressed radially against a stop. If the pressure within the rotor base chamber 88, 90 changes from the operating point, the balancing weights 72, 74 shift to at least one radial pressure position.

[0032] It should be clear that the scope of protection is not limited to the described embodiment, but various modifications are conceivable. For example, the balancing weights 72, 74, the compressor housing 10, or the compressor unit 58 can be designed differently.

Claims

1. Electric scroll compressor comprising a compressor housing (10) comprising a compressor inlet (4) and a compressor outlet (6), a compressor unit (58) comprising a driven eccentric unit (50), a fixed scroll (62), and an orbiting displacement scroll (60) arranged on the eccentric unit (50) and interacting with the fixed scroll (62), an electric motor (22) comprising a stationary stator (24) and a rotating rotor (26), wherein the eccentric unit (50) is attached to the rotor (26), and wherein at least one balancing weight (72, 74) is arranged on the rotor (26), and a high-pressure chamber (68) which is arranged in fluidic communication between the compressor outlet (6) and the compressor unit (58), characterized in that the balancing weight (72, 74) is arranged on the rotor (26) such that it can be displaced radially and the rotor comprises a rotor pressure chamber (88, 90) which is at least radially defined by the balancing weight (72, 74) and is fluidically connected to the high-pressure chamber (68), wherein the balancing weight (72, 74) is radially positionable in dependence of a pressure existing in the rotor pressure chamber (88, 90).

2. Electric scroll compressor according to claim 1, characterized in that a back-pressure chamber (69) adjoining the displacement scroll (60) is provided, which is fluidically connected to the high-pressure chamber (68) via a gas connecting channel (70), wherein the rotor pressure chamber (88, 90) is fluidically connected to the high-pressure chamber (68) via the back-pressure chamber (69).

3. Electric scroll compressor according to claim 2, characterized in that the rotor pressure chamber (88, 90) is fluidically connected to the back-pressure chamber (69) via a gas-guiding duct (92), wherein the gas-guiding duct (92) is formed in the rotor (26).

4. Electric scroll compressor according to one of the preceding claims, characterized in that the balancing weight (72, 74) is arranged on an axial end side of the rotor (26).

5. Electric scroll compressor according to one of the preceding claims, characterized in that the balancing weight (72, 74) is arranged in a radial basic position by means of a prestressed spring element (84, 86) and is arranged in at least one radial pressure position as a function of the pressure existing in the rotor basic chamber (88, 90).

6. Electric scroll compressor according to one of the preceding claims, characterized in that a rotor pressure chamber element (76) is provided with a bottom, a top and a plurality of side walls, which is arranged on an axial end face of the rotor (26), wherein the balancing weight (72, 74) is guided radially by the side walls.

7. Electric scroll compressor according to claims 5 and 6, characterized in that the spring element (84, 86) is a compression spring arranged between the balancing weight (72, 74) and the bottom or a tension spring arranged between the top and the balancing weight (72, 74), such that the balancing weight (72, 74) is loaded radially inwards by the compression spring or the tension spring.

8. Electric scroll compressor according to one of the preceding claims, characterized in that a first balancing weight (72) and a second balancing weight (74) are provided, wherein the first balancing weight (72) is arranged on a first axial end face of the rotor (26) and the second balancing weight (74) is arranged on a second axial end face, which is opposite the first end face, wherein both balancing weights (72, 74) are arranged on the rotor (26) so as to be radially displaceable, are each adjacent to a rotor pressure chamber (88, 90) and can be radially positioned as a function of a pressure existing in the respective rotor pressure chamber (88, 90).