DK145999B - COOLING MACHINE - Google Patents

Description

145999 ♦

The invention relates to a refrigeration machine in which a compressor and its drive motor are arranged in a hermetically sealed capsule, a heating device intended for evaporating liquid refrigerant which accumulates in the lower part of the capsule 5 and one in the presence of the liquid refrigerant. responsive locking device that prevents the engine from starting until the liquid refrigerant in the capsule has substantially evaporated.

In a known cooling machine of this kind (US-PS 3 744 267) a three-phase motor can be connected to voltage via a switching device if a monitoring circuit finds that the liquid level is below a predetermined level. The monitoring circuit has a thermistor which is continuously heated. When the liquid level rises during collection of liquid refrigerant and touches the thermistor, a strong evaporation of the refrigerant and thus a corresponding cooling of the thermistor takes place.

As soon as this cooling no longer takes place, ie the refrigerant has evaporated, the locking is eliminated and the engine is switched on. This construction prevents the compressor from carrying liquid refrigerant, so that the associated difficulties, especially fluid shocks, which could destroy seals and other machine parts, cannot occur. However, it presents difficulties in supplying the amount of heat required for the evaporation of the refrigerant so that there are not too large time distances available between the switching on of the cooling machine 25 and the start of the engine. Only for thermistors used as a temperature sensor can 145999 2 be kept small; but with them no appreciable heat output can be transferred. If, on the other hand, a noticeable heat output is to be transmitted, the thermistor must be chosen so large that its placement in the capsule is made more difficult.

In other known refrigeration machines (U.S. Pat. Nos. 3,107,843 and 3,411,313) an oil heater is provided to prevent mixing of the oil with the refrigerant. Engaging the engine is only possible after a predetermined oil temperature has been reached. Here, too, there is the problem that a small heating device can lead to very large delay times and that a large heating device cannot fit in the capsule.

Furthermore, refrigeration machines (US-PS 2 219 199) are known, whose motor has a drive winding and a starting winding, whereby a capacitor and a usual starting coupling are arranged, in series 15 with the starting winding, which opens after the start. Precautions for the disposal of liquid refrigerant before starting are not provided.

The invention has for its object to provide a cooling machine of the type described in the introduction, in which there are no difficulties with the arrangement of the heating device in the capsule.

This object is solved according to the invention in that the engine has a drive winding, a starting winding and an associated starting device, and that the heating device is formed by means of at least one motor winding. can be energized by switching on the cooling machine.

With this construction no additional heating device is needed, because this is formed by an already existing motor winding. This use of the motor winding is possible because, despite the presence of the locking device, it can be connected to voltage when the cooling machine is switched on. A further advantage lies in the fact that a relatively large heat output can be supplied over the motor windings, since they must be laid out for the motor output without further ado. Therefore, even larger amounts of liquid refrigerant can evaporate in a relatively short time without the need for additional space in the capsule.

It is particularly advantageous when the heating device is formed by means of the travel winding. The drive winding is dimensioned thick-wire and can carry a relatively large current. After the start, this current drops sharply, so that the heating effect is also completed.

It is furthermore advantageous when the locking device is formed by means of a contact means lying in series with the starting winding.

In another embodiment, the locking device grips the contact of the starting device. For example, in the case of a starting relay, which is controlled by the travel winding current, the contact function can be prevented by means of the locking device until the limit temperature is reached.

In the cases described, the start is prevented by not supplying power to the start winding. In this case, only the drive winding serves as a heating device. However, the locking device can also take other forms, for example it can be designed as a motor lock. In this case, both windings would cause the heating. In some cases it is also conceivable to effect the heating by means of the starting winding and to interrupt the circuit of the travel winding by means of the locking device.

The invention is explained in more detail below with the aid of exemplary embodiments shown in the drawing, which show in fig. 1 is a schematic view of a cooling machine according to the invention, FIG. 2 is a schematic section of a variation and FIG. 3 is a schematic section of a further embodiment.

In FIG. 1, a cooling machine 2 is arranged in a capsule 1, which 5 has a compressor 3 and an asynchronous motor M. The compressor 3 sucks gaseous refrigerant from the suction space 4 of the capsule and transports it over a pressure pipe 5 with an associated pressure line 6 to a condenser. After condensation, the refrigerant reaches a suction line 7 via a choke point and an evaporator in gaseous state via the suction line 7.

The asynchronous motor M has a travel winding 8 and a starting winding 9.

A main switch 10, eg a cold room thermostat, serves the switch-on. A starting device 11 is in the form of a relay with a relay winding 12 which is in series with the travel winding 8 and a relay contact 13 which is in series with the starting winding 9. In the common return line there is arranged a winding thermostat 14 which reacts and opens when the winding temperature becomes too high. The cooling machine described for this is known. In addition, a locking device 15 in the form of a bimetal switch is arranged in the starting branch, which only closes when a limit temperature of eg 50 ° C is exceeded, so that the asynchronous motor M can only start when this temperature is exceeded.

This gives the following operating mode: When the main switch 10 is switched on, the blocking current flows over the travel winding 8.

25 This heats up and heats the motor and thus the capsule suction chamber 4. The relay 11 already pulls when switched on. However, no start occurs as the bimetallic switch 15 is still open. Only when the refrigerant condensate has evaporated and the limit temperature is exceeded does this bimetal switch also close, at which point the start begins. The only at this moment effective lasting. compressor therefore transports only gaseous refrigerant.

Fluid stroke cannot occur.

In the embodiment according to fig. 2, the starting device II is located in the suction chamber. The locking device 16 hereby takes the form of a bimetal with a nose 17, which engages under the relay contact 13, which in the resting state is pressed upwards by means of a spring (not shown). Under the influence of heat, the bimetallic strip bends to the right, so that the relay switch 13, despite magnetization of the winding 12, can only be pulled when the limit temperature has been reached.

In the embodiment according to fig. 3, a locking device 18 is provided, which has a float switch 19, the float 20 of which floats on the liquid sump 21 in the bottom of the capsule 1. The float switch can, for example, be formed as a pivotable mercury contact. In the position shown, the liquid has a greater height than the predetermined height H. As a result, the float switch 19 is open. The 15 greater height means that in addition to a predetermined amount of oil, liquid refrigerant must also be present in the sump.