DE102021119660A1 - Compressor for a refrigeration cycle - Google Patents

Abstract

A compressor system (1) for a refrigeration circuit, comprising a motor housing (4) with a drive motor and a crankcase (5) with a reciprocating compressor, the drive motor and the reciprocating compressor being connected via a shaft, and in a bottom area of the crankcase (5 ) an oil pan is arranged should enable reliable cooling without impairing the mechanical stability. For this purpose, the compressor system (1) includes a cooling fan (7) whose air outlet is directed towards the oil pan.

Description

The invention relates to a compressor for a refrigeration circuit, comprising a motor housing with a drive motor and a crankcase with a reciprocating compressor, the drive motor and the reciprocating compressor being connected via a shaft, and an oil pan being arranged in a bottom region of the crankcase.

A refrigeration cycle is a system designed to cool down a piece of equipment to a desired level, such as a food freezer. A refrigerant that is moved in the closed circuit undergoes various changes in its physical state one after the other: the gaseous refrigerant is first compressed by a compressor. In the subsequent heat exchanger, it condenses while releasing heat. The liquid refrigerant is then expanded due to the pressure change via a throttling element, for example an expansion valve or a capillary tube. In the downstream second heat exchanger (evaporator), the refrigerant evaporates while absorbing heat at a low temperature (evaporative cooling). The cycle can now start all over again.

The process must be kept going from the outside by supplying mechanical work (drive power) via the compressor. For this purpose, the compressor usually has a motor housing with a drive motor. Furthermore, the compressor includes a crankcase with the actual compressor part, often a reciprocating compressor, with the drive motor and the reciprocating compressor being connected via a shaft. The crankcase and motor housing can also be designed in one piece, i.e. the drive motor and reciprocating compressor can be located in a common housing. Oil is used as a lubricant in the compressor.

Since comparatively high temperatures can prevail in the compressor, especially when additional uses such as heat pumps are integrated in the refrigeration circuit, the reciprocating compressor in the crankcase in particular is often actively cooled. For this purpose, a cooling fan is usually provided on the cylinder head. To fix it, some screws of the cylinder head are loosened and a frame for the cooling fan is mounted here.

The problem here is that the removal of screws on the cylinder head can result in stability and tightness problems.

It is therefore the object of the invention to specify a compressor system of the type mentioned at the outset, which enables reliable cooling without impairing the mechanical stability.

This object is achieved according to the invention in that the compressor system comprises a cooling fan whose air outlet is directed towards the oil pan.

The invention is based on the consideration that, in order to maintain the mechanical stability of the compressor, no screws should be loosened on the cylinder head, but cooling should be accomplished in some other way. Since the cooling essentially serves to regulate the oil temperature, since the viscosity of the oil is too low when the temperature is too high or too low, this cooling should be introduced at a point where it can have an effective effect on the oil. Therefore, cooling should be provided on the oil pan, which is located in the bottom area of the compressor. A cooling fan should be arranged here, the air outlet of which is directed towards the oil pan.

Advantageously, the cooling fan includes a number or a plurality of fans. This can be, for example, simple industrial fans in the form of fans, e.g. with a diameter of 140 mm. In this case, the axes of the fans are directed towards the oil pan.

Furthermore, the cooling fan is advantageously arranged below the oil pan. Since the compressor is often mounted on a frame such as a machine stand, the cooling fan or fans can be located below the oil pan and mounted in this frame. The air flow is therefore directed onto the oil pan from below. In addition, the air flowing around the oil pan has a cooling effect on the lower side walls of the crankcase.

The axes of the fans of the cooling fan are advantageously inclined at an angle of at most 30° to the vertical. This means that cooling can take place vertically from below, but also slightly inclined, especially in combination with several fans. Depending on the shape of the oil pan, a symmetrical arrangement of several fans can be advantageous.

The compressor system described advantageously has a reciprocating piston compressor which has centrifugal lubrication or sump lubrication. With centrifugal lubrication, a finger or disc mounted on the shaft smashes through the oil filling, thus pushing the oil through the crankcase, with sump lubrication, there is a separate oil pump that pumps the oil to the points to be lubricated. In both cases but there is an oil pan that can be cooled by the fans described.

The compressor system further includes a frame on which the motor housing, crankcase and cooling fan are mounted. This results in a particularly simple and compact installation of the system. The frame is usually made of metal and forms a stable bearing in the manner of a machine frame.

In a particularly advantageous embodiment, the compressor system is designed to use carbon dioxide as a refrigerant. Since the pressures in the compressor when using carbon dioxide as a refrigerant are higher than with conventional refrigerants, the problem of the mechanical stability of the cylinder head is particularly evident here. In addition, heat pumps are often used as an additional use in carbon dioxide systems, since the compressed gas temperatures are high. Cooling the oil pan from below reduces losses, since the oil is primarily cooled and not the compressed gas, which is used for heat recovery. The described cooling of the oil pan is therefore of particular advantage in the case of compressor systems with carbon dioxide as the refrigerant.

A system advantageously comprises a plurality of compressor systems connected in parallel as described, and a control unit, with a first of the compressor systems being formed by the control unit as a speed-controlled lead compressor, and the remaining compressor systems being switched on and off by the control unit as required. Such a combination of compressors connected in parallel can also operate larger refrigeration circuits. The lead compressor is speed-controlled, while the slave compressors are only switched on and off at a fixed speed as required.

The advantages achieved with the invention are, in particular, that the cooling of a compressor for a refrigeration circuit on the oil pan does not require any mechanical modifications to the cylinder head and the mechanical stability is not impaired by the cooling. Thanks to the cooling of the oil in the oil pan, good temperature regulation of the oil and thus optimum viscosity are achieved.

• 1 eine Seitenansicht eines Verdichtersystems mit Kühlung der Ölwanne, und
• 2 eine Frontansicht des Verdichtersystems.

An embodiment of the invention is explained in more detail with reference to drawings. Show in it:

• 1 a side view of a compressor system with cooling of the oil pan, and
• 2 a front view of the compressor system.

Identical parts are provided with the same reference symbols in all figures.

The 1 shows a compressor system 1 in a side view. The 2 shows the compressor system 1 in front view. The compressor system 1 comprises a cylindrical motor housing 4 in which a drive motor, not shown in detail, is arranged for driving the compressor. A motor connection box 2 for connecting the motor is arranged on the motor housing 4 .

A likewise cylindrical crankcase 5 with a slightly larger diameter adjoins the cylindrical motor housing 4 concentrically. A reciprocating piston compressor (not shown in detail) is arranged in the crankcase 5 and is connected to the drive motor via a crankshaft and is thereby driven by it. Cylinder heads 3 are arranged in pairs on the crankcase 5 and are aligned over the cylinder heads of the reciprocating compressor.

In an alternative embodiment, not shown, the motor housing 4 and the crankcase 5 are constructed in one piece, i.e. the drive motor and reciprocating compressor are arranged in a common housing.

The reciprocating compressor has oil lubrication. In a first embodiment, this is designed as centrifugal lubrication, in a second embodiment as sump lubrication with an oil pump. In both cases, an oil pan is arranged at the bottom of the crankcase 5 . In the reciprocating compressor, carbon dioxide is compressed as a refrigerant.

Engine housing 4 and crankcase 5 are supported on a frame 6 by four posts. In order to cool the oil in the crankcase without modifying the cylinder head 3, a cooling fan 7 is arranged in the bottom area of the compressor system 1, under the crankcase 5, the air flow of which is directed towards the oil pan, i.e. upwards. Depending on the embodiment, the cooling fan 7 can consist of one or more industrial fans, the axis of which is directed vertically or inclined upwards. The air flow thus cools the oil pan and the lower sides of the crankcase 5.

The cooling capacity of the cooling fan 7 is regulated via the speed of the fan or fans by a control unit that is not shown in detail. With the described cooling, the temperature of the oil can be reduced by approx. 20 K. This increases the viscosity of the oil and extends the service life of the compressor.

Reference List

1

compressor system

2

motor junction box

3

cylinder head

4

motor housing

5

crankcase

6

Frame

7

cooling fan

Claims (9)

Compressor system (1) for a refrigeration cycle, comprising a motor housing (4) with a drive motor and a crankcase (5) with a reciprocating compressor, the drive motor and the reciprocating compressor being connected via a shaft, and in a bottom region of the crankcase (5) an oil pan is arranged, wherein the compressor system (1) comprises a cooling fan (7) whose air outlet is directed towards the oil pan. Compressor system (1) according to claim 1 , wherein the cooling fan (7) comprises a number of fans. A compressor system (1) according to any one of the preceding claims, wherein the cooling fan (7) comprises a plurality of fans. Compressor system (1) according to one of the preceding claims, in which the cooling fan (7) is arranged below the oil pan. Compressor system (1) according to claim 4 , in which the axes of the fans of the cooling fan (7) are inclined at an angle of maximum 30° to the vertical. Compressor system (1) according to one of the preceding claims, in which the reciprocating compressor has centrifugal lubrication or sump lubrication. Compressor system (1) according to any one of the preceding claims, further comprising a frame on which motor housing (4), crankcase (5) and cooling fan (7) are mounted. Compressor system (1) according to one of the preceding claims, designed for the use of carbon dioxide as refrigerant. System, comprising a plurality of parallel-connected compressor systems (1) according to one of the preceding claims and a control unit, wherein a first of the compressor systems (1) is formed by the control unit as a speed-controlled lead compressor, and the remaining compressor systems (1) by the control unit as required - and be switched off.

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