JP4305979B2 - Variable capacity displacement type capacity compressor operation method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a variable capacity operation method for a variable displacement positive displacement compressor, and more particularly to an operation method for increasing energy efficiency in a wide range of capacity operation.
[0002]
[Prior art]
A conventional variable displacement positive displacement compressor that uses both the discharge frequency variable means and the displacement volume variable means, as described in JP-A-1-167477, for the purpose of expanding the variable capacity range. It has been devised. The discharge frequency variable means is realized by limiting the drive source of the compressor to an electric motor and driving the inverter. In the variable capacity operation method, in the capacity variable range that can be driven by the inverter, the volume variable means fixes the displacement volume to the maximum, and in the low speed operation range where the inverter drive becomes difficult or impossible, that is, in the small capacity operation range. Only the above-described displacement volume variable means is used to reduce the displacement volume and shift to a high-speed rotation operation region where inverter drive is possible.
[0003]
As a result, small-capacity operation, which was impossible with inverter drive alone, became possible, and the capacity variable width could be expanded. However, with such an operation method, the energy efficiency of the motor and the inverter is reduced when the motor is driven at low speed near the lower limit of the inverter drive with the maximum displacement volume, compared with the high speed operation, and the compression including the inverter is performed. There was a problem that the energy efficiency of the entire section was greatly reduced.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to solve the above problems and provide a compressor operating method with high energy efficiency even in a wide capacity operation.
[0005]
[Means for Solving the Problems]
As means for achieving the above object, the displacement volume variable means capable of changing the displacement volume to a plurality of stages or an infinite stage, and the discharge capable of changing the discharge frequency of the compressed gas discharged from the compression chamber to a plurality of stages or an infinite stage. In the variable capacity operation method of the variable displacement positive displacement compressor provided with the frequency variable means, the plurality of units that secure the same capacity during operation of a capacity that can be realized by combining a plurality of conditions of the displacement volume and the discharge frequency. There is a time for comparison operation to perform at least two operations of the above condition combinations, and sudden change of required operation capacity including stop and start of operation period after the comparison operation until the next comparison operation In the stable operation time excluding accompanying transient operation, the displacement volume of the operation with a small amount of energy per unit time required for the operation in the comparative operation. It was operating method for setting the displacement volume varying means.
[0006]
If the displacement volume is changed by a factor of 0.5 when operating at a certain capacity, in order to ensure the same capacity as before the change, the performance of the displacement volume variable means is somewhat Although there is a deviation, it is necessary to double the discharge frequency of the compressed gas by the discharge frequency variable means. If the drive source is a synchronous motor and the inverter is driven, this corresponds to doubling the command rotation frequency of the inverter. As described above, when the displacement volume varying means and the discharge frequency varying means are used in combination, a plurality of combinations of the displacement volume and the discharge frequency can be realized within a certain capacity range.
[0007]
The means for achieving the object is to operate with a combination of a plurality of displacement volumes and discharge frequencies per unit time when operating at a capacity that can be realized by a plurality of combinations of the displacement volume and the discharge frequency as described above. Compare the amount of energy. As a result, this is an operation method in which an operation with a small amount of energy per unit time required for the operation is selected after the comparison time. As a result, there is an effect that high energy efficiency operation can be realized in a wide capacity operation range.
[0008]
By the way, in a stable operation period excluding start-up and stop-out of a series of operation periods that start and stop, the operating conditions required for the compressor fluctuate and are represented by the temperature of each part of the compressor. The state that changes. Therefore, the appropriate value of the displacement volume changes even during a series of operations.
[0009]
This means sets the comparative operation periodically or irregularly during a series of operations, and checks and sets the appropriate displacement volume in each operation state, thereby improving the energy efficiency of the series of operation periods. It has the effect of increasing the proportion of high operating periods.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment in which the present invention is applied to the operation of an inverter-driven variable capacity scroll compressor used as a compressor for a refrigeration cycle will be described with reference to FIGS. 1 is a configuration diagram of a refrigeration cycle, FIG. 2 is a longitudinal sectional view of a compressor, FIG. 3 is a longitudinal sectional view of a variable displacement check valve, FIG. 4 is a longitudinal sectional view of a differential pressure control valve, and FIG. FIG. 6 is a plan view from the scroll wrap side of the fixed scroll member, and FIG. 7 is a cross-sectional view of the engagement state of both scroll members at the start of compression when the displacement volume is reduced. 8 is a longitudinal sectional view of the bypass valve, and FIG. 9 is a graph showing the relationship between the command frequency of the inverter and the capacity of the compressor.
[0011]
First, the variable capacity scroll compressor will be described with reference to FIG. First, the structure will be described.
[0012]
The orbiting scroll member 3 has a scroll wrap 3b standing on the end plate 3a, and a bearing holding portion 3s into which an orbiting bearing 3w is inserted and orbiting Oldham grooves 3g and 3h. Then, a surface treatment with good lubricity and conformability is applied to at least the wrap side of the end plate 3a and the entire area of the scroll wrap 3b.
[0013]
The fixed scroll member 2 is provided with a non-turning reference surface 2u which is the same surface as the scroll wrap tooth tip surface, and a peripheral groove 2c is formed there. A plurality of flow grooves 2r through which the motor wire 19n passes and the discharge gas and oil flow are provided on the outer periphery. Then, two capacity variable holes 2h, two bypass holes 2e, a discharge hole 2d, and a back surface side conduction path 2β are provided at positions of the tooth bottom as shown in FIGS.
[0014]
A variable capacity check valve 41 shown in a Q portion surrounded by a two-dot chain line circle in FIG. 2 is incorporated in the upper part of the variable capacity hole 2h, and a bypass valve 23 is incorporated in the upper part of the bypass hole 2e. A differential pressure control valve 100 shown in a P portion surrounded by a two-dot chain line circle in FIG. 2 is incorporated in the upper portion of the conduction path 2β. Further, a communication groove 2δ and a suction dig 2q are provided on the outer edge side of the tooth bottom surface, and a suction hole 2v is provided from the back side.
[0015]
The suction pipe 54 is inserted into the suction hole 2v. At that time, the suction valve body 24a and the suction check valve spring 24c are inserted to form the suction check valve 24.
[0016]
Here, the capacity variable check valve 41, the differential pressure control valve 100, and the bypass valve 23 incorporated in the fixed scroll member 2 will be described with reference to FIGS. First, the variable capacity check valve 41 will be described. A capacity variable valve dig 2g is opened from the opposite side of the capacity variable hole 2h, and a capacity variable valve seal surface 2i having a semicircular longitudinal section is provided at the bottom. The capacity variable valve body 41a having a diameter slightly smaller than the diameter is inserted into the capacity variable valve excavation 2g, and one end of the capacity variable valve spring 41c is attached to the spring positioning protrusion 41h of the capacity variable valve cap 41f. It is press-fitted, bonded or welded to 2 g of the variable capacity valve digging. At this time, a perfect seal is made between the outer periphery of the variable capacity valve cap 41f and the variable capacity valve excavation 2g. Further, the displacement variable valve spring 41c is compressed and presses the displacement variable valve body 41a against the displacement variable valve seal surface 2i.
[0017]
Next, the differential pressure control valve 100 will be described. A differential pressure control valve excavation 2f is opened from the opposite side of the back side conduction path 2β, a differential pressure control valve seal surface 2j having a semicircular longitudinal cross section at the bottom, and a suction side through which a side surface is connected to the communication groove 2δ. A conduction path 2α is provided. After inserting the differential pressure control valve body 100a having a diameter slightly smaller than the diameter into the differential pressure control valve digging 2f, one end of the differential pressure control valve spring 100c is attached to the spring positioning protrusion 100h of the differential pressure control valve cap 100f. In this state, the pressure control valve excavation 2f is press-fitted, bonded or welded.
[0018]
At this time, a perfect seal is made between the outer periphery of the differential pressure control valve cap 100f and the differential pressure control valve dig 2f. The differential pressure control valve spring 100c is compressed and presses the differential pressure control valve body 100a against the differential pressure control valve seal surface 2j. Finally, the bypass valve 23 will be described. A bypass valve excavation 2κ is opened from the side opposite to the bypass hole 2e, and a bypass valve seal surface 2λ having a semicircular longitudinal section is provided at the bottom.
[0019]
A bypass valve body 23a having a diameter slightly smaller than the diameter is inserted into the bypass valve excavation 2κ, and the bypass valve excavation is performed with one end of the bypass valve spring 23c attached to the spring positioning protrusion 23h of the bypass valve cap 23f. Press fit or bond or weld to 2κ. At this time, it is not necessary to completely seal between the outer periphery of the bypass valve cap 23f and the bypass valve digging 2κ. The bypass valve spring 23c is compressed and presses the bypass valve body 23a against the bypass valve seal surface 2λ.
[0020]
The frame 4 is provided with a fixed mounting surface 4b for mounting the fixed scroll member 2 on the outer peripheral portion, and a turning sandwiching surface 4d on the inner side. Further on the inner side, frame Oldham grooves 4e and 4f (both not shown) are provided in order to place the Oldham ring 5 between the frame 4 and the orbiting scroll member 3. A shaft seal 4a and a main bearing 4m are provided at the center, and a shaft thrust surface 4c for receiving the shaft is provided on the scroll side. A plurality of flow grooves 4h serving as gas and oil flow paths are provided on the outer peripheral surface. And one of them passes the motor wire 19n.
[0021]
The Oldham ring 5 is provided with frame protrusions 5a and 5b (both not shown) on one surface, and swivel protrusions 5c and 5d on the other surface.
[0022]
The shaft 12 is provided with a shaft oil supply hole 12a, a main bearing oil supply hole 12b, a shaft seal oil supply hole 12c, and a sub-bearing oil supply hole 12i. Further, there is a balance holding portion 12h having an enlarged diameter at the upper portion thereof, and a shaft balance 49 is press-fitted there. Further, an eccentric portion 12f is provided.
[0023]
The rotor 15 incorporates a non-magnetized permanent magnet 15b in a laminated steel plate 15a and is provided with rotor balances 15c and 15p at both ends. The stator 16 has a plurality of stator grooves 16c and stator holes serving as a flow path for compressive gas and oil in the outer peripheral portion and inside of the laminated steel plate 16a.
16m is provided.
[0024]
These components are assembled as follows. First, the shaft 12 is inserted into the main bearing 4a of the frame 4, and the rotor 15 is press-fitted or shrink-fitted. Further, the Oldham ring 5 is mounted on the frame 4 by inserting the frame protrusions 5a and 5b of the Oldham ring 5 into the frame Oldham grooves 4f and 4e.
[0025]
Further, the orbiting scroll member 3 is inserted into the orbiting Oldham grooves 3g and 3h while the orbiting protrusions 5c and 5d of the Oldham ring are inserted, and the eccentric portion 12f of the shaft 12 is inserted into the orbiting bearing 3w. Mount on surface 4d.
[0026]
As a result, the orbiting bearing upper chamber 95 is formed at the center of the back surface of the orbiting scroll member 3, and the orbiting back chamber 99 is formed around it. The fixed scroll member 2 is engaged with the orbiting scroll member 3, and the fixed scroll member 2 is fixed to the frame 4 by a wrap fixing screw 52 at a position where the rotational torque becomes a permissible value or less while rotating the shaft 12. At this time, the thickness of the end plate 3a is set to be smaller by about 0 to 10 μm than the distance between the swivel and sandwich surface 4d and the non-turn reference surface 2u.
[0027]
Here, since the wrap side of the end plate 3a has a conformable surface treatment film, the surface treatment film is scraped off during operation, and the distance between the swiveling and scissoring surface 4d and the non-turning reference surface 2u and the end plate 3a. The difference in thickness is about 10 to 20 μm. If this gap is too small, the sliding loss will increase during operation and the overall heat insulation efficiency will be reduced if it is too narrow. A problem arises in that normal compression cannot be started because the pulling force cannot be increased to a required magnitude in the axial direction.
[0028]
Next, the assembly portion is inserted into the cylindrical casing 31 in which the stator 16 is pre-fitted and the bearing support plate 18 is welded, and the discharge pipe 55 is inserted into a predetermined groove of the frame 4. The assembly part is welded to the cylindrical casing 31, and then the discharge pipe 55 is welded to the cylindrical casing. Thus, a motor 19 is formed by the rotor 12 and the stator 16, and a motor chamber 62 is formed between the bearing support plate 18 and the frame 4.
[0029]
Next, the bearing housing 70 is incorporated so that one end of the shaft 12 coming out from the central hole 18 c of the bearing support plate 18 is inserted into the cylindrical hole of the spherical bearing 72 mounted on the bearing housing 70, and the rotation of the shaft 12 is performed. The position of the bearing housing 70 is adjusted while detecting the torque, and the bearing housing 70 is welded to the bearing support plate 18 at a position where the rotational torque is below an allowable value. Then, an oil supply pipe 71 is press-fitted into the lower end portion of the shaft oil supply hole 12a. Since the bearing housing 70 is disposed in a dead space at the center of the auxiliary bearing side coil end portion 16x of the stator 16, the volume of the oil storage chamber 80 is increased, and the oil level is kept low even when a predetermined amount of oil is introduced. Therefore, there is an effect of suppressing the amount of discharged oil.
[0030]
Further, since the shaft can be shortened, the weight is reduced and the distance between the main bearing 4m and the sub-bearing 72 is shortened, so that the natural frequency of the rotating portion including the shaft 12, the orbiting scroll member 3 and the rotor 15 can be increased. There is an effect that a compressor with less vibration and noise can be provided. Further, since the welded portion that fixes the bearing housing 70 to the bearing support plate 18 is separated from the spherical bearing 72, the spherical bearing portion is not deformed by the welding, and the clearance of the spherical bearing becomes uniform. In addition to improving the reliability of the shaft 12, it is possible to smoothly suppress the shaft 12 from touching around the main bearing portion during high-speed rotation, and vibration and noise generated from the spherical bearing portion at that time. There is a specific effect that can be reduced.
[0031]
Next, the joining pipe 36 is press-fitted or brazed to the two capacity variable valve caps 41f fixed to the opposite wrap surface of the fixed scroll 2 to secure a seal. Here, the connecting pipe 36 and the variable capacity valve cap 41f may be connected by the fixed scroll member 2 alone.
[0032]
And the hermetic terminal 22, the suction pipe mounting pipe 37, and the merging pipe mounting pipe
The upper casing 20 to which 35 is welded is inserted into the cylindrical casing 31 after the motor wire 19 n is connected to the inner terminal of the hermetic terminal 22. Then, a current is passed from the external terminal of the hermetic terminal to the stator 16 to magnetize the permanent magnet 15b in the rotor 15, and the motor 19 is a synchronous motor.
[0033]
Then, the bottom casing 21 having the magnet 89 supported and fixedly arranged by the magnet holder 89 a is welded to the lower end of the cylindrical casing 31 to form the oil storage chamber 80. Further, the suction pipe 54 is press-fitted into the suction hole 2v through the suction pipe attachment pipe 37, and the variable capacity pipe 33 is press-fitted into the junction pipe 36 through the variable capacity pipe attachment pipe 35. Complete the press-fit seal. Then, after the upper casing 20 is welded to the cylindrical casing 30 to form the fixed back chamber 61, the gap between the suction pipe mounting pipe 37 and the suction pipe 54, the capacity variable pipe mounting pipe 35, and the capacity variable pipe. Braze the gap 33 to complete the seal.
[0034]
Next, the capacity variable connection pipe 58, the suction bypass pipe 38 to which the suction connection pipe 56 is connected, and the discharge pressure introduction pipe 39 to which the discharge connection pipe 57 is connected are connected to the switching valve 34, and three of the pipe bodies are connected. Are connected to the pipes 54, 55, 33.
[0035]
Next, the operation will be described. First, the steady operation will be described.
[0036]
As the motor 19 rotates, the shaft 12 rotates and the orbiting scroll member 3 orbits. Here, since the Oldham ring 5 is provided, rotation of the orbiting scroll member 3 is prevented. By this operation, the compressible gas in the suction chamber 60 enters the compression chamber 6 formed between the scroll members, is compressed, and is discharged to the fixed back chamber 61 from the discharge hole 2d.
[0037]
In an overcompression condition in which the pressure ratio that is the ratio of the discharge pressure to the suction pressure is lower than the appropriate pressure ratio that is determined by the volume ratio that is the ratio of the compression chamber volume at the time of discharge to the displacement volume, the bypass valve 23 shown in FIG. When the pressure in the compression chamber 6 becomes equal to or higher than the discharge pressure by operating, the bypass valve body 23a moves upward to allow the compressible gas to escape to the fixed back chamber 61, thereby suppressing overcompression. Here, the bypass valve spring 23c provides a trigger for moving the valve body 23a downward when the bypass valve is closed, so as to avoid a delay in closing the bypass valve 23 and avoid a decrease in volume efficiency. The pressing force applied to the bypass valve body 23a is set weak.
[0038]
When this setting is increased, the bypass valve 23 is opened only when the pressure in the compression chamber rises by a pressure corresponding to the set value. Therefore, the effect of suppressing overcompression is reduced, and the overall adiabatic efficiency, which is energy efficiency, is reduced. Invite. The compressible gas discharged into the fixed back chamber 61 enters the motor chamber 62 through the fixed scroll member 2 and the flow grooves 2r and 4h on the outer periphery of the frame 4.
[0039]
The compressible gas entering the motor chamber 62 cools the motor 19 while passing through the stator groove 16c and the stator hole 16m from the upper part to the lower part. In the process, the compressible gas collides with each part of the motor 19 and separates the oil contained therein. The separated oil falls to the lower part of the motor chamber 62 and is stored in the oil storage chamber 80 through an oil drain hole 18 a in the outer peripheral portion of the bearing support plate 18. Thereafter, the compressible gas returns to the upper part again through the stator groove 16c and the stator hole 16m, and exits to the outside through the discharge pipe 55 and the discharge connection pipe 57.
[0040]
Next, the process from the start-up until the above-described steady operation will be described. After the thickness of the end plate 3a of the orbiting scroll member 3 is about 0 to 10 μm at the time of assembling the surface treatment film of the orbiting scroll member 3 than the interval between the orbiting surface 4d and the non-orbiting reference surface 2u. Is reduced by about 10 to 20 μm, and the gap between the tooth roots of the wraps is enlarged by this distance at the time of activation.
[0041]
When the clearance is such a degree, by setting the turning speed of the orbiting scroll member 3 to a size allowed at the time of starting, it is possible to raise the discharge pressure and the suction pressure to some extent. Since the pressure in the oil storage chamber 80 is substantially the discharge pressure, and the pressure in the revolving back chamber 99 is always lower than the discharge pressure, the stored oil in the oil storage chamber 80 is mainly due to this pressure difference, and the revolving bearing 3w It flows into the turning back chamber 99 through the gap between the shaft seal 4a and the main bearing 4m.
[0042]
At this time, the compressible gas dissolved in the oil is gasified by the reduced pressure, and the pressure in the swirling back chamber 99 is increased. As a result, the orbiting scroll member 3 is pressed against the fixed scroll member 2. In this case, the swirling back chamber 99 is cut off from the suction chamber 60, so that the pressure in the swirling back chamber 99 increases rapidly. However, the differential pressure control valve 100 causes the differential pressure control valve spring to exceed the suction pressure. When the pressure reaches a certain value determined by the amount of compression of 100c (hereinafter referred to as an excessive suction pressure value), the compressive gas and oil escape to the suction chamber 60 through the differential pressure control valve 100, and the pressure rise Stop.
[0043]
After such a process, the operation shifts to steady operation. As described here, except for the transient operation at the time of start-up, the pressure in the swirling back chamber 99 is always maintained at the suction pressure + the excessive suction pressure value. As a result, since the orbiting scroll member 3 is pressed against the fixed scroll member 2 with an appropriate force under various operating conditions, the gap between the tooth tip bottoms of the scroll wrap is reduced to suppress leakage loss, Since the friction loss between the two end plates can be reduced, there is a specific effect that operation with high energy efficiency is possible.
[0044]
Next, the variable capacity means will be described. Since the discharge frequency variable means of the compressor is realized by driving the inverter of the motor 19, the description thereof will be omitted, and the displacement volume variable means will be described using the variable capacity check valve 41 of FIG. Here, since the synchronous motor is used as the motor, the discharge frequency becomes the same as the command frequency of the inverter, and there is no need to monitor the actual discharge frequency, and there is a specific effect that the controllability is improved. In this embodiment, the displacement volume is changed in two stages. When the displacement volume is set to a larger one, the switching valve 34 causes the displacement variable pipe 33 to communicate with the discharge introduction pipe 39, and when the displacement volume is set to a smaller one, the switching valve 34 causes the switching valve 34 to communicate with the discharge introduction pipe 39. The variable capacity pipe 33 is communicated with the suction bypass pipe 38. Each of these cases will be described below.
[0045]
When the switching valve 34 is set to the discharge introduction pipe 39 side, discharge pressure is applied to the upper surface of the capacity variable valve body 41a, so that the switching valve 34 is normally closed. Therefore, since the displacement volume does not decrease, it is set to the larger one. Here, the valve 41 opens only when the pressure on the compression chamber 6 side becomes higher than the discharge pressure, and the compressible gas goes out to the cycle as the discharge gas. This is the same operation as the bypass valve 23 described previously.
[0046]
As can be seen from FIG. 6, since the variable capacity check valve 41 is provided on the outer peripheral side of the bypass valve 23, there is a specific effect of acting as a low pressure side bypass valve. Here, the capacity variable valve spring 41c provides a trigger for moving the valve body 41a downward when closing, so as to avoid a delay in closing the capacity variable valve 41 and avoid a decrease in volume efficiency. The pressing force given to the capacity variable body valve 41a is set weak.
[0047]
When this setting is increased, the bypass valve 23 is opened only when the pressure in the compression chamber rises by a pressure corresponding to the set value. Therefore, the effect of suppressing overcompression is reduced, and the overall adiabatic efficiency, which is energy efficiency, is reduced. Invite. Furthermore, the variable capacity check valve 41 at this time also has a unique effect of avoiding liquid compression and lowering reliability due to lap breakage. Of course, the bypass valve 23 has the same effect of avoiding liquid compression. Further, when this variable displacement check valve 41 performs the liquid compression avoidance operation, the liquid goes directly out of the compressor through the pipe, so that the fixed scroll member 2 is not cooled from the outside of the scroll wrap.
[0048]
For this reason, since the temperature of the wrap forming the suction chamber 60 rises in a short time and the refrigerant flowing in with the liquid can be gasified, the specific effect that the duration of liquid compression can be shortened and the reliability can be improved. There is. In general, in the refrigeration cycle, when the operating pressure ratio is low, the discharge frequency is also reduced at the same time. Therefore, when the variable pressure check valve 41 acts as a bypass valve, the required valve opening / closing frequency is low, so that the closing delay does not occur even if the lift amount of the valve is increased. Therefore, in order to make it at least larger than the lift amount of the bypass valve 23, the gap between the lower surface of the spring positioning projection 41h and the displacement variable valve seal surface 2i is set to be larger.
[0049]
By doing so, the flow resistance in the direction of coming out from the compression chamber 6 side of the valve can be reduced, so that overcompression can be further suppressed without lowering the volume efficiency. As a result, there is a specific effect that the total heat insulation efficiency is increased. In this way, liquid compression can be avoided easily, and there is a specific effect that the risk of lap breakage can be further reduced.
[0050]
When the switching valve 34 is set to the suction bypass pipe 38 side, the upper surface of the capacity variable valve body 41a is at the suction pressure. Therefore, while the capacity variable hole 2h looks into the compression chamber 6, the pressure may increase. Since the capacity variable valve 41 is opened and the compressible gas returns to the suction pipe via the switching valve 34, the pressure in the compression chamber maintains the suction pressure. The capacity variable hole 2h is provided at a position where it begins to look into the compression chamber before the compression chamber starts to be closed, and continues to be removed from the compression chamber until the volume of the compression chamber is reduced to a desired displacement volume. is there. As a result, the compression starts when the capacity variable hole 2h is removed from the compression chamber, and the displacement volume can be reduced.
[0051]
FIG. 7 is an engagement state diagram of both wraps at the start of compression when the displacement volume is set to a smaller one, and both the A2 and B2 chambers in the drawing are the chambers in which the compression is started. Compared with the case where the capacity variable hole 2h is closed, the start of compression is delayed by about one rotation, so that the displacement volume is significantly reduced. On the other hand, A1 and B1 are in a state where the closing ends in a while, but since the capacity variable hole 2h is viewed before the closing ends, the compression does not start. By the way, setting the pressing force of the orbiting scroll member 3 against the fixed scroll member 2 becomes a problem when the displacement volume is changed to a smaller one.
[0052]
In the conventional method in which a back pressure hole is made in the end plate part of the orbiting scroll member to apply a pressing force by applying intermediate pressure to the orbiting back chamber, the position of the back pressure hole is optimized when the displacement volume is not changed. Normally, the pressure in the swirling back chamber is close to the suction pressure. For this reason, the orbiting scroll member cannot be pressed against the fixed scroll member, and a normal compression operation cannot be realized. Therefore, it is practically impossible to employ this capacity control means. If it is intended to be adopted, the change width of the displacement volume must be made very small, and the original purpose of greatly expanding the capacity control width cannot be achieved.
[0053]
In this embodiment, since the differential pressure control valve 100 is used, the pressure in the swirling back chamber 99 basically depends only on the suction pressure, and does not change by changing the displacement volume. Therefore, there is a specific effect that normal compression can be performed without causing the pressing force of both scroll wraps to be insufficient as in the conventional method using the back pressure hole.
[0054]
By the way, the differential pressure control valve cap 100f of the differential pressure control valve 100 shown in FIG. 4 is bent when the difference between the discharge pressure and the suction pressure, which is the upper and lower pressure difference, is large, You may make it the material or shape which has the rigidity of the grade which changes a super-suction pressure value to about 10-30%. If it does in this way, when the differential pressure | voltage of suction and discharge is small, the tendency for the pressing force between both scroll members to become small will come out.
[0055]
If the displacement volume is reduced, the force by which the scroll members 2 and 3 are separated by the compressed gas is reduced, so that the appropriate pressure in the orbiting back chamber is generally smaller than before the displacement volume is changed. Since the differential pressure between the discharge pressure and suction pressure during small-capacity operation is generally small, a differential pressure control valve that changes the over-suction pressure value will reduce the displacement volume. When the condition is changed to a smaller value, the excessive suction pressure value decreases, so that it is possible to avoid an excessive pressing force between the scroll members, and there is a specific effect that reliability and total heat insulation efficiency are improved. is there.
[0056]
Next, an operation method in the refrigeration cycle of the variable capacity scroll compressor described so far will be described with reference to FIGS.
[0057]
First, a general operation method of the compressor will be described with reference to FIG. 1 in relation to the operation method of the refrigeration cycle. The compressor is operated by being supplied with electric power from the inverter 201 connected to the power source 203 through the inverter input line 204 through the compressor input line 202. The compressible gas boosted by the operation of the compressor is supplied to the cycle non-compression unit 200 including a heat exchanger and an expansion valve through the discharge connection pipe 57. The supplied gas returns from the non-compression unit 200 to the compressor through the suction connection pipe 56.
[0058]
In this way, a refrigeration cycle is formed. In order to control this refrigeration cycle, the cycle sensor signal line 205 and the compressor sensor signal line 207 fetch the state quantities of the cycle non-compression unit 200 and the compressor into the signal processing unit 201a in the inverter, respectively.
[0059]
The signal processing unit 201a determines the control content for each unit from these pieces of information, and controls the electric power controlled by the compressor input line 202, the cycle input line 206, and the switching valve input line 208, respectively. Power is supplied to the control target and switching valve drive source 209 in the unit 200. Here, the control target in the cycle non-compression unit 200 having an individual drive power supply is a method in which only the cycle signal line 210 is connected and a control signal is transmitted thereby to control individual drive sources. .
[0060]
This method is suitable when the distance between the signal processing unit 201a and the control target is large. This is because if the drive current is passed for a long distance, electromagnetic waves or the like are generated to adversely affect the signal line or the risk of fire due to a short circuit increases. For example, when the compressor is separated, a separate drive power supply may be provided in the switching valve drive source 209, and only a signal for controlling it may be sent from the inverter 201.
[0061]
Next, variable capacity operation will be described. First, a schematic relationship between the combination of the discharge frequency and the displacement volume in each capacity operation will be described with reference to FIG. In this embodiment, since a synchronous motor is used, the command frequency and the discharge frequency of the inverter coincide. Therefore, the command frequency of the inverter is used instead of the discharge frequency. Since the two-stage displacement volume of the present embodiment is a ratio of 3: 2, the ratio of the inverter command frequency having the same capacity is 2: 3.
[0062]
In addition, since there is an upper limit for the power supplied to the inverter, an upper limit appears for the capacity that can be operated. Since the required power varies depending on the pressure condition even at the same discharge frequency, the upper limit of the capacity varies depending on the pressure condition. From the above, the range that can be actually operated is the range indicated by the thick line. However, this relationship is based on the assumption that the volumetric efficiency is constant, and is actually somewhat different.
[0063]
As a tendency, the volume efficiency becomes higher as the displacement volume is smaller. The reason is that the flow path returning to the suction pipe 54 through the variable capacity hole 2h always has a flow resistance, so that compression occurs during the operation of the variable capacity hole 2h, and the pressure is slightly higher than the suction pressure. . Therefore, it is because it was paid that much.
[0064]
Another reason is that the time required for compression is shortened because the rotational speed is increased, and internal leakage is suppressed. Further, as described above, since the pressure in the orbiting back chamber 99 is controlled to the suction pressure + a constant value, the pressing force of the back orbiting scroll member 3 to the fixed scroll member 2 is increased, and the gap between the tooth roots is added. Another reason is that the internal gap is suppressed by reducing the gap. Thus, the actual relationship between the inverter command frequency and the capacity when the displacement volume is small tends to shift upward as shown by the dotted line.
[0065]
The upper limit value of the capacity is lower in the normal design than when the displacement volume is large. The reason is described below. The friction loss of the bearing portion is not greatly affected by the bearing load, but is roughly proportional to the square of the rotational frequency of the shaft 12, so that even if the capacity is the same, the displacement volume at which the rotational frequency of the shaft 12 is on the high speed side. The loss of the small bearing portion is generally larger than that of the large displacement volume, and the difference between the two increases at an accelerated rate as the rotational frequency of the shaft 12 increases.
[0066]
Therefore, in the large capacity region where the rotational frequency of the shaft 12 is high, the power consumption of the small displacement volume is larger than that of the large displacement volume, and reaches the upper limit value of the supplied power at a small capacity level. It is. As a result, in the large capacity area of A and the small capacity area of C in the figure, operation is possible only with one type of large displacement volume and small displacement volume, respectively. Operation with a displacement volume is possible.
[0067]
In this embodiment, during the operation in this capacity range, the operation is actually performed with both displacement volumes, the electric power consumed at that time is examined in the inverter, and the operation with the displacement volume with the smaller power consumption is performed. The operation method is performed until the next comparative operation. As a result, there is an effect that high energy efficiency operation can be realized in a wide capacity range.
[0068]
Next, the above comparative operation method will be described in detail. First, a method for setting the comparative operation time will be described.
[0069]
Although the relationship in FIG. 9 varies depending on the pressure condition, the pressure condition of the normal refrigeration cycle is determined almost uniquely with respect to the command frequency of the inverter. A suppression volume / command frequency graph, which is a relationship of the command frequency for each suppression volume with respect to the capacity as shown in FIG. 9 in consideration of this relationship, is stored in the signal processing unit 201a. During operation, the input power of the compressor is constantly monitored, and when the allowable power value is reached, if the displacement volume at that time is set to be small, the displacement volume is changed to be large. When the displacement volume is large, control is performed so as not to increase the input power, and a mode in which comparison operation cannot be performed is set. Further, the command frequency of the inverter is constantly monitored, and when the minimum command frequency is reached, if the displacement volume at that time is set to be large, the displacement volume is changed to be small.
[0070]
At start-up, set the volume to be large. When the required value given to the refrigeration cycle changes at start-up, the signal processing unit 201a gives a command to each part of the power module or refrigeration cycle in the inverter with the required value at that time as a target. It becomes driving. The rotation speed of the compressor also changes. When the cycle approaches stable operation, the signal output from the signal processing unit 201a also changes less. Therefore, whether or not the operation of the compressor is stable is determined based on whether or not the command rotational speed has become constant.
[0071]
Specifically, it is monitored whether or not the command rotational speed changes within a predetermined time, for example, a stability determination time such as 3 minutes. Here, if the command frequency of the compressor is equal to or less than the preset fluctuation range in the stability determination time, it is determined whether or not the operation at that time is within the capacity range B shown in FIG.
[0072]
When the displacement volume is large, it is determined whether or not the command frequency is equal to or lower than the α determination frequency in FIG. 9, and when it is equal to or lower, the comparison operation is started. As long as the required value given to the refrigeration cycle does not change at these times, a stability determination is made at a predetermined time interval (hereinafter referred to as a comparative operation time interval), and the necessity of similar comparison operation is determined and determined. Follow the instructions.
[0073]
On the contrary, when the displacement volume is small, it is determined whether or not the command frequency is equal to or higher than the β determination frequency in FIG. 9, and when it is higher, the comparison operation is started.
[0074]
At the following times, as long as the required value given to the refrigeration cycle does not change, a stability determination is made after the comparative operation time interval, and it is determined whether or not a similar comparative operation is necessary, and is executed according to the determination. Here, when the command frequency in the B capacity region is higher, the bearing loss is much larger when the displacement volume is small, where the rotational frequency of the shaft is large. Therefore, the α ′ determination frequency is lower than the α determination frequency. It is better to use.
[0075]
Accordingly, unnecessary comparison operation can be avoided, so that there is a specific effect that a highly efficient operation time can be extended. Further, the comparative operation time interval may be set to a time proportional to the previous displacement volume invariant time.
[0076]
In this way, since a comparative operation interval can be set according to the necessity of the comparative operation in a series of operations, in an operation that does not require a change in displacement volume, such as performing a continuous operation without changing the required value for the cycle, a comparison is made. There is a specific effect that the operation time is almost eliminated and the highly efficient operation time can be extended. Moreover, you may provide the operation mode which restrict | limits the frequency | count of comparative operation from the time of starting for such an operation | movement.
[0077]
Next, an operation method during the comparative operation will be described. When it is determined that the comparative operation is necessary, the input power to the compressor at that time is stored. And the command frequency which becomes the same capacity | capacitance with the presser volume which is not the present setting from the stored presser volume / command frequency graph is calculated | required, and the operation | movement is performed. After the stability determination, the input power to the compressor is checked and compared with the stored input power value. Then, the operation with the smaller power value is started. Here, a method in which the stability determination is not performed during the comparison operation may be used. In this case, there is a specific effect that the comparison time is short.
[0078]
Further, in this driving method, it is preferable to make a current priority determination that the driving is not changed unless the value becomes lower by a certain ratio than the input at the time of driving so far. This is because when the accuracy of the displacement volume / command frequency graph is low, the comparison is made with the power at different capacities, and the accuracy of the power consumption in the comparison operation is low.
[0079]
Next, a second embodiment in which a switching valve is attached to each of the two capacity variable check valves will be described with reference to FIG. Since there are cases where the capacity variable stage changes the capacity of only one compression chamber and the case where two compression chambers are used, the same as in the first embodiment, except that it becomes a three-stage displacement volume variable means. Therefore, the description of the configuration and operation is omitted. As a result, there is a specific effect that even higher energy efficiency operation can be realized in a wide capacity range.
[0080]
In addition, since the capacity variable connection pipe 58 is linear, the capacity variable valve cap 41f can be connected after the upper casing is press-fitted. Two capacity variable holes may be provided at different positions of the compression chamber volume. If it becomes like this, it will become a four-stage displacement volume variable means, and there exists a peculiar effect that operation of still higher energy efficiency is realizable in a wide capacity range.
[0081]
【The invention's effect】
According to the present invention, there is an effect that a compressor operating method with high energy efficiency can be provided in a wide capacity operation.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a refrigeration cycle of a first embodiment.
FIG. 2 is a longitudinal sectional view of the variable capacity scroll compressor of the first embodiment.
FIG. 3 is a longitudinal sectional view of a check valve for a variable capacity pipe of the compressor of the first embodiment.
FIG. 4 is a longitudinal sectional view of a differential pressure control valve of the compressor of the first embodiment.
FIG. 5 is a plan view of the fixed scroll member of the compressor of the first embodiment from the side opposite to the scroll wrap.
FIG. 6 is a plan view from the scroll wrap side of the fixed scroll member of the compressor of the first embodiment.
FIG. 7 is a cross-sectional view of both scroll wraps at the start of compression when the displacement volume of the compressor of the first embodiment is reduced.
FIG. 8 is a longitudinal sectional view of a bypass valve of the compressor of the first embodiment.
FIG. 9 is a graph showing the relationship between the command frequency of the inverter of the first embodiment and the capacity of the compressor.
FIG. 10 is a longitudinal sectional view of a variable capacity scroll compressor according to a second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 2 ... Fixed scroll member, 2e ... Bypass hole, 2h ... Variable capacity hole, 3 ... Orbiting scroll member, 34 ... Switching valve, 42 ... Variable capacity check valve, 100 ... Differential pressure control valve, 110 ... Variable displacement mechanism .

Claims (1)

A displacement volume variable means capable of changing the displacement volume to a plurality of stages or an infinite stage, and an inverter having a discharge frequency variable means capable of changing the discharge frequency of the compressed gas discharged from the compression chamber to a plurality of stages or an infinite stage. In the variable capacity operation method of the variable displacement positive displacement compressor provided,
The inverter is
A comparison operation time for performing at least two actual operations among the plurality of condition combinations for securing a similar capacity during actual operation of a capacity that can be realized by a plurality of condition combinations of the displacement volume and the discharge frequency. Provided,
Storing the input power to the compressor during the comparative operation;
In the stable operation time excluding the transient operation in the operation period from the comparison operation to the next comparison operation, the push-out volume of the actual operation with a small input power required for the actual operation is compared with the push-out volume of the actual operation. A variable displacement operation method for a variable displacement positive displacement compressor, characterized in that a variable displacement volume means is set.

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