JPH0421071B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to cooling of a rotor of a motor in a sealed electric compression device for a refrigeration compressor.
Sealed electric compression equipment integrates a sealed electric motor and a refrigeration compressor into a completely sealed system, eliminating refrigerant leakage from the shaft sealing device on the drive shaft of the compressor to the outside air, and preventing failures that occur in the shaft sealing device. The idea was to completely eliminate the maintenance that would result from this.

In this case, the inside of the housing of the compressor and the inside of the electric motor that drives the compressor are configured to communicate with the refrigerant at least at the shaft portion. There is no problem with cooling the stator coils in the refrigerant because the cooling occurs from the outer periphery of the stator core, but with regard to cooling the rotor, (a) the amount of heat generated by the rotor is Emission is due to heat conduction through the common axis, and (b) radiation from the rotor surface to the stator side.
(c) This is due to the convection of the heat medium surrounding the rotor, and the effect of (c) occupies a large proportion and has a great influence on the operating state. That is, the temperature of the rotor increases and becomes high, which causes even the dilute refrigerant gas to decompose.

As larger capacity devices become available, this cooling becomes an even more important issue. This is because during operation when the temperature of the object to be cooled is low, the evaporation pressure of the refrigerant gas will be low, and if an extremely low temperature is required, the system will approach a vacuum state. Regarding the cooling of the rotor by convection in such a refrigerant gas atmosphere, the relationship between the gas pressure and the temperature rise of the rotor in the negative pressure range where the gas pressure is below atmospheric pressure and the vacuum state is determined by the relationship between the gas pressure and the temperature rise of the rotor. As the temperature decreases, the temperature rise of the rotor increases, and as the vacuum state approaches, it becomes increasingly difficult to dissipate heat from the rotor, causing the temperature to rise rapidly.

The effect on pressure and temperature rise above atmospheric pressure is extremely small. The above-mentioned problems in the negative pressure range naturally do not occur in the conventional structure where the electric motor and compressor are separated, but the problem only occurs when the two are integrated and the negative pressure is large. It is a point. Needless to say, this is because the two are integrated and have a structure in which the shaft portions simply communicate.

Therefore, it is necessary to increase the internal pressure on the motor side to the range of refrigerant gas pressure that allows convection in response to the large negative pressure on the compressor side, and for this purpose, it is necessary to create a pressure difference between the motor and the compressor. It will not happen.

The present invention was made in view of these points,
This will be explained with reference to the diagram.

FIG. 1 is a schematic diagram of a cooling system of a sealed electric compressor, in which 1 is a sealed electric motor, 2 is a driven compressor, and both are integrated and sealed. 3 is the rotation axis and 11
1 is a rotor of the electric motor, 12 is a stator, 13 is a stator coil, and 14 is a conducting wire connected to a power source through a switching circuit, so that electric power is supplied to the electric motor 1. 15 is a load power sensor.

21 is a refrigerant condenser, and the refrigerant compressed by the compressor 2 is cooled here, liquefied, and stored in a liquid receiver 22. 23 is an expansion valve that supplies refrigerant to the cooler 24. Here, heat is exchanged with the object to be cooled and it becomes gas.
It is sucked into the compressor 2 to form a cooling system.

Further, a rotor temperature sensor 31 attached to the rotor 11 extracts a signal from the sensor using a signal output device 32 consisting of a sliding ring, a brush, etc., and inputs the signal to a regulator 33. Alternatively, the output of the load power sensor 15 may be input to the regulator 33, or a pressure sensor may be provided in the electric motor 1 to input this signal.

The refrigerant control valve 34 is controlled by control outputs corresponding to these inputs, and refrigerant is fed into the electric motor 1. In the case of this figure, the compressor 2 and the electric motor 1 are communicated through a bearing portion 25. If the refrigerant gas pressure inside the casing of the compressor 2 reaches the vapor pressure corresponding to the cooling load and decreases, the refrigerant gas pressure inside the motor 1 will also decrease, causing problems in cooling the rotor 11. When the pressure is reached, the output of the refrigerant control load power sensor 15 or the rotor temperature sensor 31 is input to the regulator 33, and the control valve 34 sends the refrigerant into the motor 1, so that the pressure is close to the specified pressure. held under pressure. However, in this case, the communication phenomenon through the bearing part 25 is small, and the amount of heat generated in the rotor 11 is carried into the compressor 2 housing through the bearing part 25, but most of it is caused by the fixation of the motor 1 due to convection. It is carried to the child frame, which further dissipates it into the atmosphere. Therefore, there is no problem even if a small amount of refrigerant flows in through the bearing section serving as the communication section.

The details of this communication portion 26 are shown in FIG. Figure A is a schematic diagram of a contact type isolation mechanism, where 35 is a sliding ring that is attached to the shaft 3 and rotates, 36 is a fixed ring that is stationary and attached to the housing of the compressor 2, and a spring 37 is attached to the sliding ring 35. Pressed by Thereby, pressure can be maintained on the sliding surfaces of the sliding ring 35 and the fixed ring 36 against the differential pressure on both sides.

Therefore, the refrigerant gas surrounding the rotor 11
1, and heat is radiated to the outside through the stator core and stator frame by gas convection.

The isolation mechanism in this case is different from the shaft sealing device of a conventional open compressor, which aims to completely seal and shut off the refrigerant, allowing leakage and at the same time ensuring that no failure occurs during operation. , the structure must focus on simplifying the structure.

Therefore, during operation, the refrigerant gas pressure inside the electric motor 1 is controlled by the control system including the sensors 15 and 31, the regulator 33, and the control valve 34.

The figure below shows an example of a non-contact isolation mechanism, which is a labyrinth type. 38 is a labyrinth type shaft sealing mechanism with a slight gap between the rotating shaft and the stationary part, and fins are provided on the bearing side. It may also be a labyrinth type in which a large number of fins and expansion chambers are alternately provided on the rotating shaft side. With this mechanism, there are no sliding or friction surfaces, so there is no wear or damage, and even if there is a leak of refrigerant gas, which is unique to the labyrinth type, it will flow into the compressor 2 casing, and this will be prevented. In an appropriate amount, it can even be a good thing. In addition to this, there is also a non-contact type screw type shaft sealing mechanism, which can also be used. In either case, the structure must be simple and failure-free.

As described above, the present invention provides a sealed electric compressor in which a compressor and an electric motor are integrated, and is provided with an isolation mechanism that allows leakage at the boundary between the compressor and the electric motor, especially when negative pressure is applied on the compressor side. This system controls the pressure of the refrigerant gas that surrounds the rotor when it becomes difficult to cool the rotor of the motor, and the refrigerant liquid does not cool by forced gas circulation. This prevents abnormal temperature rises in the rotor, eliminates the troubles caused by this, and ensures stable operation.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of the cooling system of a sealed electric compressor, Fig. 2 is a schematic diagram of a contact type isolation mechanism, and b is a schematic diagram of a non-contact type isolation mechanism. 1: Electric motor, 2: Compressor, 3: Drive shaft, 11:
Rotor, 15: Load power sensor, 31: Rotor temperature control sensor, 33: Regulator, 34: Control valve, 35: Sliding ring, 36: Fixed ring, 38: Labyrinth type shaft sealing mechanism.

Claims (1)

[Scope of Claims] 1. An electric compression device in which a refrigeration compressor and an electric motor are integrated and sealed, including a function of maintaining a necessary differential pressure between the compressor and the electric motor, and a rotor of the electric motor. A method for cooling a sealed electric compressor, the method comprising: controlling the pressure of a refrigerant gas surrounding the rotor in response to a rise in temperature of the rotor. 2. Cooling of a sealed electric compression device according to claim 1, characterized in that the refrigerant gas pressure surrounding the rotor can be set to a permissible value for the maximum temperature rise of the rotor caused by the load of the electric motor. Method. 3. Claim 1, characterized in that the boundary is a bearing part where the refrigeration compressor and the electric motor are connected by a shaft, and an isolation mechanism is provided on both sides of the bearing part to maintain a differential pressure of the refrigerant gas. Cooling method for sealed electric compressor.