KR20000063059A - A method of reducing the noise produced by a scroll compressor of a heat pump system and an apparatus for controlling the scroll compressor - Google Patents

Abstract

The present invention relates to a scroll compressor for use in a heat pump system having a solenoid operated four-way flow reversing valve. The processor monitors system parameters to indicate that a flow reversal is occurring or is about to occur, where the compressor motor is driven by a low pressure differential across the compressor, causing the compressor to produce some undesirable noise caused by the detachment of scroll elements. It is interrupted for a period of time. At the end of this cycle, the compressor motor is turned on again. The processor is arranged to cycle the compressor at the beginning and end of each thawing cycle or when the operating mode of the system changes.

Description

A method of reducing noise caused by a scroll compressor of a heat pump system, and a control device of the compressor.

TECHNICAL FIELD The present invention relates to heat pumps and more particularly to heat pump systems using scroll compressors.

The use of scroll compressors is well known and is widely accepted in the art due to the many advantages provided by this type of compressor. While scroll compressors work well in heat pump systems, they can generate noise when the operating mode of the system changes. This often occurs during the heating mode of operation when the system controller requires a defrost cycle.

Testing has confirmed that compressor noise occurs when the pressure difference between the compressor's trajectory scroll and the fixed scroll is low enough to allow the scroll elements to separate. This occurs during a short period of time after the four-way reversing valve has been cycled to reverse the direction of refrigerant flow through the system. After the flow reversal occurs, it takes about 20 or 30 seconds to stabilize the system, after which it will return to relatively quiet normal operation.

Accordingly, it is an object of the present invention to improve the heat pump.

This object is achieved in a heat pump system using a scroll compressor to eliminate unwanted noise when the flow of refrigerant through the system is reversed, especially when the system has to perform a thawing cycle during the heating mode of operation. The processor is programmed to detect the reversal of refrigerant flow as the system's four-way reversing valve is cycled. The sensed signal is analyzed and processed so that when the flow reversal begins or is in progress, the processor shuts down the compressor for a sufficient period of time to allow the system to stabilize, thereby eliminating unwanted compressor noise typically generated during the start of the flow reversal cycle.

BRIEF DESCRIPTION OF DRAWINGS To make it easier to understand these and other objects of the present invention, reference will be made to the detailed description of the invention in conjunction with the accompanying drawings.

1 is a schematic diagram showing a heat pump using a scroll compressor embodying the technical idea of the present invention.

2a to 2d show a fixed relationship of scroll elements of a compressor used in the system shown in FIG. 1 showing a compression method.

Figure 3 is a schematic flow diagram of controlling the operation of the compressor to remove unwanted compressor noise when the direction of refrigerant flow through the system is reversed.

<Explanation of symbols for main parts of drawing>

10: heat pump system

12: compressor

20: 4-way flow reversing valve

21: Actuator

25: processor

40, 41: scroll element

34: sealed pocket

1 schematically shows a heat pump system 10 embodying the technical idea of the present invention. The system uses a scroll compressor to deliver refrigerant to the outdoor heat exchanger or coil 14 via line 11 when operating in the cooling mode. In the cooling mode, the outdoor coil operates as a condenser and the condensed refrigerant passes through the refrigerant line 17 to the indoor heat exchanger or coil 16. The expansion device 15 is mounted in the refrigerant line and throttles the high pressure refrigerant passing through the line at a lower pressure. In the cooling mode, the indoor coil acts as an evaporator to draw heat from the indoor air to cool it. The refrigerant vapor generated by the indoor coil then passes through the line 18 to the inlet side of the compressor.

The suction line 24 and discharge line 23 of the compressor are connected to a four-way flow reversing valve 20 which is cycled by a solenoid actuator 21 to reverse the flow of refrigerant through the system when the operating mode of the system is changed. Connected. The solenoid actuator is controlled by the processor 25 and specifically cycles the valve when the system is in the heating mode of operation. At this time, the high pressure refrigerant from the compressor is sent to the room coil 16 which now acts as a condenser in the system to heat the room air. The outdoor coil then acts as an evaporator to draw heat from the outside air. The expansion device 15 is arranged to automatically throttle the refrigerant moving in any direction through the cooling line.

The thermal sensor 30, which provides temperature related data to the system processor 25, is coupled to the outdoor coil 14. Temperature data is processed and analyzed when the system is in heating mode to determine the start of the thawing cycle. As is known, the system is thermally reversed during the thawing cycle, and the outdoor coil acting as a condenser causes the heat exchanger to heat up to melt frost or ice from the coil surface, which reduces the efficiency of the system.

As will be described in detail later, the processor is programmed to provide an input signal to the solenoid actuator 21 when determining that a thawing cycle should be started. This then cycles the four-way valve to reverse the flow of refrigerant through the system.

As noted above, it has been found that reversal of flow through a heat pump can provide undesirable noise in a scroll compressor. The scroll compressor operates as shown in FIGS. 2A-2D by moving the sealing pocket 34 of the refrigerant from the low pressure region shown in FIG. 2A to the high pressure region shown in FIG. 2D. The sealing pocket of fluid is surrounded by two end plates, fixed scroll element 40 and moving scroll element 41. One plate 37 supports the fixed scroll element 40, while the other plate (not shown) supports the trajectory scroll element 41. The scroll elements are aligned along the parallel axis so that the sealed pocket moves as shown to trap the refrigerant in a volume that constantly decreases as the trajectory scroll moves in rolling contact with the fixed scroll. Although not shown, inlet and outlet ports are provided to move the refrigerant into and out of the moving pocket area.

It has been found that the trajectory and fixed scroll elements of the compressor can be separated when low pressure differentials occur across the compressor. All scroll compressors are basically prone to temporary scroll detachment when low pressure differentials are to occur. Experiments have shown that as soon as the four-way flow reversing valve is cycled, for example at the beginning and end of the thawing cycle, a period of low pressure differential that lasts for about 20 seconds occurs. During this period, the scroll elements are separated due to flow instability that causes unwanted noise.

As noted above, the processor 25 receives temperature related data about the outdoor coil 14 from the sensor 30 and processes the information to determine when the thaw cycle begins and ends. To begin the thaw cycle when the heat pump is operating in the heating mode, a signal is sent to the solenoid actuator 21 which cycles the four-way valve 20 to reverse the refrigerant flow through the system. At this time, the outdoor coil operates as a condenser without air flow, so that the frost formation on the coil melts. When the thawing operation is complete, the processor signals the solenoid actuator again to cycle the four-way valve, and the system returns to normal heating mode again.

Thus, during each flow reversal cycle, at the beginning and end of the thawing cycle, the pressure differential across the compressor is low resulting in unwanted noise. The processor is further programmed to shut off the compressor motor 13 (Fig. 1) for a predetermined time at the beginning and end of each thawing cycle. When it is determined that the thaw cycle is to begin or end, the processor sends a signal to the motor switch 27 (FIG. 1) to shut off the compressor motor for about 30 seconds. At the end of this 30 second period, the processor signals the motor switch again to start the compressor motor again. By shutting off the compressor for a short time at the beginning and end of each thawing cycle, undesirable noise is eliminated during this unstable period.

3 is a flow chart showing the steps performed by the processor at the beginning and end of each thawing cycle or at any time when the flow of refrigerant through the system is reversed. The processor reads and stores data about the solenoid actuator voltage to determine when the system is in heating mode. When in heating mode, the four-way valve is set to the first position and the solenoid actuator stops operating. Thus, a voltage of 0 V is applied across the solenoid terminal. For example, at the beginning of the thawing cycle, 24 volts is applied to the solenoid terminals and the solenoid is operated to cycle the four-way valve.

The stored data is used to determine when the flow direction of the refrigerant passing through the four-way valve 20 is reversed. Processor 25 senses the voltage level value of the input signal across the input terminal of solenoid 21 and compares the detected voltage level of the input signal with the voltage level of the input signal in the previous mode of operation. For example, when the heat pump system 10 operates in the heating mode, the input signal to the solenoid 21 has a voltage level of 0V. This value is stored in memory by the processor 25 as shown in block 80. The processor 25 continuously monitors the input signal as shown in block 82. When the processor 25 detects a change in the voltage level of the input signal as shown in block 84, the processor 25 performs sampling of the input signal for 0.5 seconds to confirm that a change in the voltage level of the input signal has occurred. Perform (see blocks 86 and 88). Thus, in this embodiment, the processor 25 reads the voltage level of the input signal N times in 0.5 seconds and compares the sampled voltage level with the voltage level of the input signal stored in the memory (in this case, 0 V). If the processor 25 determines that M of the N samples are now 24 volts indicating a change in the voltage level of the input signal, then the processor 25 indicates that the thawing cycle has begun or the operating mode of the system has changed. It is known that the compressor motor 13 is stopped for a predetermined time, usually for 30 seconds. These steps are shown in blocks 90, 92, 94. The above-described procedure is also used to determine when to stop the compressor motor 13 when returning from the cooling or thawing mode back to the heating mode. It will be appreciated that the input signal may have a different voltage level than that described in this embodiment.

As shown in block 96, after the compressor motor 13 is stopped for a predetermined time, the processor 25 automatically operates the compressor motor 13 and causes it to start up again. Processor 25 then resets the 30 second timer shown in block 98 and stores the new input voltage value in memory as shown in block 80.

As may be apparent to those skilled in the art, other methods may be used to determine the timing for stopping the compressor 12. For example, as described above, there is a sudden change in the discharge pressure and the suction pressure when the mode of the heat pump system 10 changes. Accordingly, it is possible to monitor the discharge pressure and the suction pressure to determine the time point for stopping the compressor 12. In addition, the voltage obtained by the compressor motor 13 changes when the discharge pressure changes. Therefore, it is possible to monitor the voltage obtained by the compressor motor 13 in order to determine the time point for stopping the compressor 12. Similarly, the temperature of the outdoor coil can also provide sufficient input data to the processor that can start and stop the compressor motor.

By using the heat pump system of the present invention, it is possible to eliminate unwanted noise when the flow of refrigerant through the system is reversed, especially when the system performs a thawing cycle in the heating mode of operation.

Claims (11)

A method of reducing noise generated by a scroll compressor used in a heat pump system having a four-way flow reversing valve, Detecting a system parameter indicating whether a change in refrigerant flow direction through the system is occurring or is about to occur; Stopping the scroll compressor for a period of time after or after a coolant flow change has occurred Method comprising a. The method of claim 1, wherein said sensing comprises sensing a change in position of a four-way flow reversing valve of said system. The method of claim 1, further comprising providing a solenoid actuator for controlling the four-way flow reversing valve, wherein the sensing step includes sensing a voltage change across the input terminals of the solenoid actuator. Characterized in that the method. 3. The method of claim 2, further comprising providing a temperature sensor for monitoring a temperature of an outdoor coil of the system, providing an output signal indicative of the sensed temperature, and wherein the output signal is to reach one or more threshold levels. When cycling the four-way valve. 2. The method of claim 1, further comprising reactivating the compressor motor at the end of the predetermined time period. The method of claim 1, wherein the predetermined time period lasts about 30 seconds. An apparatus for controlling a scroll compressor for use in a heat pump having a solenoid operated four-way refrigerant flow reversing valve, A processor for monitoring at least one system parameter indicative of a change in refrigerant flow direction through the heat pump; Means for stopping the compressor motor for a predetermined period of time when the processor detects whether a change in the system parameter occurs or is about to occur. Apparatus comprising a. 8. The apparatus of claim 7, comprising sensing means for detecting a change in position of the four-way valve of the system and transmitting an output signal to the processor indicating an inversion of the refrigerant flow through the system. 9. The apparatus of claim 8, wherein said sensing means further comprises means for detecting an input voltage across the solenoid actuator of said four-way valve. 10. The apparatus of claim 9, wherein the processor further comprises timer means for restarting the compressor motor after the predetermined period. 11. The apparatus of claim 10, wherein the predetermined period is about 30 seconds.