JPS6235907Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an improvement of a capacity control device for a two-stage refrigerant compressor.

In a two-stage refrigerant compressor, capacity control is installed inside the compressor in order to reduce the load on the drive machine when starting the compressor, or to adjust the capacity of the compressor according to the amount of load during operation. A mechanism is installed to control capacity. Such a capacity control mechanism, as shown in FIG.
A capacity control bypass valve 3 having a valve cover 2 is attached to the holder, and this bypass valve 3 normally connects the low pressure chamber 7 to the discharge chamber 6 by the action of a spring 4 provided between it and a spring receiver 5. It is biased in the direction of communication. On the other hand, the electromagnetic valve 8 for capacity control has the function of controlling high-pressure gas supplied from a compressor (not shown) through conduits 9 and 10 into the chamber 3a formed at the head of the bypass valve 3, and when shutting off. , and has the function of releasing the pressure in the chamber 3a to the low pressure chamber 7 via the conduits 10 and 11.

When operating current is supplied to the solenoid valve 8, high pressure gas flows through the conduit 9, the solenoid valve 8 and the conduit 10.
This pressure causes the bypass valve 3 to move downward against the spring 4 to shut off the discharge chamber 6 and the low pressure chamber 7, and the compressor performs load operation. In addition, when the solenoid valve 8 is not energized, the high pressure gas produced by the compressor is shut off by the solenoid valve 8, the pressure inside the chamber 3a is guided to the low pressure chamber 7 via the conduit 11, and the bypass valve 3 is operated by the spring 4. The discharge chamber 6 rises due to the action and communicates with the low pressure chamber 7, and capacity control is performed.

FIG. 2 uses the same three solenoid valves 8a, 8b, 8c as shown in FIG.
The configuration of a two-stage refrigerant compressor having six high-stage cylinders and six low-stage cylinders indicated by the symbol L is shown. Note that 10a, 10b, and 10c correspond to the conduit 10 shown in FIG. 1, and 11a and 11b correspond to the conduit 11, respectively. The cylinder shown with diagonal lines in FIG. 2 is the capacity control cylinder. In other words, in this example, there are 6 cylinders in the low stage and 2 cylinders in the high stage, and the minimum displacement control is for the 3 cylinders in the low stage,
It will be a high stage 1 cylinder.

FIG. 3 shows a control circuit of a conventional capacity control device for controlling the capacity of the two-stage refrigerant compressor shown in FIG.
Coils a, 8b, and 8c are shown, respectively. In this circuit, when the contact 12 of the compressor operating contactor coil (not shown) is open, the timer T contact 14 is closed, and when the capacity control contact 13 is closed, the coils S1 to S3 are closed. is energized, and the solenoid valves 8a to 8c are opened. When the contact 12 is closed, the timer T is started, and the contact 14 is open for the set time, so the coils S1 to S3 are not energized and the solenoid valves 8a to 8c are closed, as shown with diagonal lines. In each of the displacement control cylinders, the discharge chamber 6 is communicated with the low pressure chamber 7, and a displacement control operation is performed.
When the set time limit of the timer T has passed, the contact 14 is closed, and if the capacity control contact 13 is closed,
The coils S1 to S3 are energized, and the solenoid valves 8a to 8c
is opened, resulting in full load operation.

In a two-stage refrigerant compressor having such a configuration, on the high stage side, the discharge chamber 6 has a high pressure and the low pressure chamber 7 has an intermediate pressure, and on the low stage side, the discharge chamber 6 has an intermediate pressure and the low pressure chamber 7 has a low pressure. Therefore, both chambers 3a of the bypass valve 3 are at high pressure. Here, the intermediate pressure of the compressor is
The relationship is determined by the high pressure (condensing temperature), low pressure (evaporation temperature), and the ratio of the number of loaded operating cylinders on the low stage side and the number of loaded operating cylinders on the high stage side of the compressor. For example, the evaporation temperature - 20 ℃, and the condensing temperature is 32℃, the intermediate pressure in the case of 6 cylinders in the low stage and 2 cylinders in the high stage is approximately 7Kg/cm2 The intermediate pressure in the case of ² gauge, 6 cylinders in the low stage and 1 cylinder in the high stage is approximately 11.5Kg /cm ² gauge. Also, the high pressure is the saturation pressure at the condensation temperature of about 11.9
Kg/cm ² gauge, low pressure is about 2.6 saturated pressure at evaporation temperature
Kg/cm ² gauge. When such a two-stage refrigerant compressor enters full-load operation from capacity control operation with three cylinders on the low stage and one cylinder on the high stage, the differential pressure between the high pressure and the intermediate pressure on the high stage side is small, causing the bypass valve to shut off. Although it takes time, the difference in high and low pressures on the low stage side is larger than on the high stage side, so the bypass valve is instantly shut off and load operation begins. For this reason, the ratio of the number of cylinders in load operation between the low stage side and the high stage side becomes large (6:1 in this example), which has the disadvantage that the intermediate pressure becomes higher and higher, making it impossible for the high stage side to enter load operation. arise.

This idea was devised to eliminate the above-mentioned drawbacks. By operating the high-stage capacity control cylinder under load before the low-stage side, the intermediate pressure is lowered and the high-stage capacity control cylinder is reliably controlled. An object of the present invention is to provide a capacity control device for a two-stage refrigerant compressor, which shuts off a bypass valve and then shuts off a low-stage bypass valve, thereby ensuring that all cylinders are operated under load. An embodiment of this invention will be described below with reference to the drawings. FIG. 4 is a circuit diagram showing a control circuit of a capacity control device according to an embodiment of this invention, which controls the capacity of a two-stage refrigerant compressor having the configuration shown in FIG.

In the circuit of Figure 4, there are two timers T and 2T.
A contact 14, which is used and opens only within a certain period of time from the start of the first timer T, is connected in series with the capacity control contact 13 and inserted between the second timer 2T and the power source. . In addition, the coil S1 is
It is connected to a power supply via a contact 16 that closes when the timer 2T starts, and coils S2 and S3 are connected in parallel with this coil S1 via a contact 15 that closes after a certain period of time from the start of the timer 2T. There is.

Now, when the contact 12 of the compression operation contactor coil (not shown) is closed, the timer T is started, and the contact 14 is opened for a fixed time period. In this state, even if the capacity control contact 13 is closed,
Timer 2T does not operate and therefore its contact 1
5 and contact 16 are both open. In this state, the coils S1 to S3 are not energized, and therefore, capacity control (3 cylinders in the low stage, 1 cylinder in the high stage) operation at the time of starting is performed. Next, when the time limit of timer T elapses, its contact 14 closes, which starts timer 2T and closes contact 16, but contact 15 remains open until the set time limit of timer 2T comes. be. Therefore, only the coil S1 is energized, and the high-stage capacity control cylinder is operated under load. That is, three cylinders on the low stage and two cylinders on the high stage are operated, and since the intermediate pressure is lower than at the time of startup, the high stage side can reliably enter into load operation.

Furthermore, when the time limit of the timer 2T elapses, the contact 15 which was open until then is closed, and the coil S2
and S3 are energized, and the lower stage side capacity control cylinder enters load operation. This causes all cylinders to perform load operation.

As described above, according to this invention, when entering load operation from capacity control operation, the high-stage capacity control cylinder first enters load operation by the timed operation of the two timers, and then after a certain period of time, the low-stage capacity control cylinder enters load operation. An action is obtained in which the side displacement control cylinder enters load operation. Therefore, the capacity control cylinder on the higher stage side can reliably shift to the loaded operating state.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view showing a part of a general capacity control cylinder, Fig. 2 is a block diagram showing the configuration of a two-stage refrigerant compressor, and Fig. 3 is a circuit showing a control circuit of a conventional capacity control device. 4 are circuit diagrams showing a control circuit of a capacity control device according to an embodiment of this invention. 3... Bypass valve, 3a... Chamber, 6... Discharge chamber, 7... Low pressure chamber, 8, 8a, 8b, 8c... Solenoid valve, S1, S2, S3... Coil, T, T2...
…timer.

Claims (1)

[Scope of utility model registration request] A first timer having a contact that opens only within a certain time period from the time of startup, a first contact that starts when the contact of the first timer is closed and closes with the startup, and a second timer having a second contact that closes after a predetermined period of time; and a second timer that operates when the first contact of the second timer closes to control a bypass valve of the high-stage capacity control cylinder. a first solenoid valve that operates when both the first contact and the second contact of the second timer are closed to control a bypass valve of the lower stage side capacity control cylinder; Capacity control device for a two-stage refrigerant compressor equipped with a valve.