Back pressure control valve and electric scroll compressor having the same

Abstract

To provide a back pressure control valve and an electric scroll compressor having the same. [Solution] The back pressure control valve for an electric scroll compressor includes a valve housing consisting of a first housing (11), a second housing (12), and a communication passage (13) connecting the first and second housings (11, 12), and a piston (14) consisting of a first piston (141) located in the first housing (11), a second piston (142) located in the second housing (12), and a connecting rod connecting the first and second pistons (141, 142), and the piston (14) is capable of moving up and down freely within the first and second housings (11, 12).

Description

[Technical Field]

[0001] The present invention relates to a back pressure control valve and an electric scroll compressor having the same. [Background technology]

[0002] A typical scroll compressor used in the refrigeration cycle of a refrigerator may have the structure shown in Figure 3. The scroll compressor includes a fixed scroll 31, an orbiting scroll 32 that orbits relative to the fixed scroll 31, a discharge space 33 through which compressed refrigerant is discharged, an inlet 34 through which refrigerant is introduced, a motor 36a for rotating the orbiting scroll 32, and a shaft 36b that rotates the orbiting scroll 32 in response to the operation of the motor 36a. The scroll compressor may also include a backpressure hole 351 or a discharge hole 352 for adjusting the pressure between the compression chamber and a backpressure chamber 35, which will be described later. In such an electrically driven scroll compressor, the backpressure chamber 35 must be formed behind the end plate of the orbiting scroll 32 to minimize leakage from the gap between the fixed scroll 51 and the orbiting scroll 32, which orbits to form a compression chamber and compress gas. The axial component of the gas force generated within the compression chamber pushes the orbiting scroll 32 away from the fixed scroll 31, increasing the axial gap between the two scrolls 31, 32. Therefore, if a back pressure chamber 35 is formed behind the end plate of the orbiting scroll 32, the internal pressure of the back pressure chamber 35 generates back pressure, which pushes the orbiting scroll 32 toward the fixed scroll 31 and reduces the axial gap. In this case, if the back pressure is smaller than the axial gas force, the orbiting scroll 32 separates from the fixed scroll 31. Conversely, if the back pressure is greater than the axial gas force, the orbiting scroll 32 is pressed tightly against the fixed scroll 31. This tight contact generates friction loss between the two scrolls 31, 32, and the greater the back pressure, the greater the friction loss. Therefore, it is necessary to create an appropriate level of back pressure that minimizes the axial gap between the two scrolls 31, 32 while simultaneously preventing friction loss from increasing beyond a predetermined level. A known method for creating back pressure in the back pressure chamber 35 is to form a back pressure hole 351 in the end plate of the orbiting scroll, thereby connecting the compression chamber on the front side of the end plate with the back pressure chamber 35 on the back side of the end plate. In this case, gas in the compression chamber flows into the back pressure chamber 35 through the back pressure hole, creating pressure in the back pressure chamber.The pressure level of the gas filling the back pressure chamber 35 is determined by the position of the back pressure hole 351. The closer the back pressure hole 351 is to the center of the orbiting scroll 32, the higher the pressure of the gas that flows into the back pressure chamber 35. While this type of back pressure hole has a simple structure, it cannot generate the appropriate back pressure corresponding to the operating conditions when the operating conditions change, resulting in excessive or insufficient back pressure. Another method for generating back pressure in the back pressure chamber is to form a back pressure hole not in the end plate surface but inside the wrap along the wrap height direction corresponding to the tip surface of the central part of the orbiting scroll wrap, extending axially to the back surface of the orbiting scroll end plate to which the wrap is vertically attached. In this case, if the back pressure in the back pressure chamber is sufficient, the tip surface of the orbiting scroll wrap is in close contact with the end plate surface of the fixed scroll, sliding and orbiting with minimal axial clearance. When operating conditions change and the back pressure becomes insufficient, the orbiting scroll separates from the fixed scroll in the axial direction. This separation creates a gap passage where the inlet of the back pressure hole formed in the tip surface of the center of the orbiting scroll wrap is separated from the end plate surface of the fixed scroll. As a result, high-pressure gas in the compression chamber located in the center flows into the back pressure hole through the opened inlet of the back pressure hole and then into the back pressure chamber. This inflow of high-pressure gas increases the pressure in the back pressure chamber, and the back pressure in the back pressure chamber becomes greater than the axial gas force, pushing the orbiting scroll back toward the fixed scroll. On the other hand, when operating conditions change such that the discharge pressure or suction pressure decreases, the excessive back pressure must be appropriately relieved, but this has the disadvantage that the appropriate back pressure reduction cannot be achieved quickly. In relation to adjusting the gap between the fixed scroll and the orbiting scroll, Patent Document 1 (International Publication No. WO 2010 / 064537) discloses a scroll compressor including an inlet that can communicate with a compression chamber, an outlet that communicates with a backpressure chamber, and a communication hole that connects the inlet and the inlet. However, the prior art has the aforementioned shortcomings. Therefore, a method is needed to minimize the gap between the fixed scroll and the orbiting scroll while quickly responding to changes in operating conditions and simultaneously providing backpressure without excessive friction loss between the orbiting scroll and the fixed scroll.However, the prior art does not disclose such a method.

[0003] The present invention is intended to solve the problems of the prior art and has the following objects. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. WO2010 / 064537 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a back pressure control valve that can provide an optimum value for the back pressure in the back pressure chamber depending on changes in operating conditions, and a scroll compressor having the same. [Means for solving the problem]

[0006] According to a suitable embodiment of the present invention, a back pressure control valve for an electric scroll compressor includes: a valve housing consisting of a first housing, a second housing, and a communication passage connecting the first and second housings; and pistons consisting of a first piston located in the first housing, a second piston located in the second housing, and a connecting rod connecting the first and second pistons; and the pistons are capable of moving up and down freely within the first and second housings.

[0007] According to another suitable embodiment of the invention, the second housing has a relatively large cross-sectional area compared to the first housing.

[0008] According to yet another suitable embodiment of the present invention, the upper cylinder of the first housing is connected to the discharge chamber, the lower cylinder of the first housing is connected to the back pressure chamber, and a first back pressure chamber communication passage is formed on the side of the first housing to communicate between the upper cylinder of the first housing and the back pressure chamber when the piston reaches bottom dead center, the upper cylinder of the second housing is connected to the suction chamber, and the lower cylinder of the second housing is connected to the back pressure chamber, and a first suction chamber communication passage is formed on the side of the second housing to communicate between the lower cylinder of the second housing and the suction chamber when the piston reaches top dead center.

[0009] According to yet another suitable embodiment of the present invention, the piston pump further includes elastic units provided in the first housing and the second housing to limit the movement of the first piston and the second piston and at the same time provide a restoring force.

[0010] According to yet another suitable embodiment of the present invention, the pressure ratio r p =(A2-A0) / A1, where A0, A1 and A2 represent the cross-sectional areas of the connecting rod, the first piston and the second piston, respectively.

[0011] According to yet another suitable embodiment of the present invention, a scroll compressor includes: a fixed scroll; a rotating scroll that rotates relative to the fixed scroll; a back pressure chamber formed on the back surface of the end plate of the rotating scroll; and a back pressure control valve according to any one of claims 1 to 5 for generating back pressure in the back pressure chamber. [Effects of the Invention]

[0012] The back pressure control valve according to the present invention provides an optimal back pressure that optimizes the axial conformance of the orbiting scroll according to the discharge pressure and suction pressure, thereby minimizing leakage and friction loss between the fixed scroll and the orbiting scroll of a scroll compressor. The back pressure control valve according to the present invention maintains the pressure in the back pressure chamber at a predetermined level in response to various changes in operating conditions, such as an increase or decrease in discharge pressure and an increase or decrease in suction pressure, by opening and closing the back pressure passage and the suction pressure passage according to the corresponding up and down movement of the piston and the position of the piston. The scroll compressor according to the present invention is applied to a refrigerator compressor and provides a highly efficient gas compression function with minimized leakage and friction loss. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a diagram illustrating an embodiment of a back pressure regulating valve according to the present invention. [Figure 2A] 4 is a diagram illustrating an embodiment of a process of adjusting the pressure of a back pressure chamber by a back pressure regulating valve according to the present invention; [Figure 2B] 4 is a diagram illustrating an embodiment of a process of adjusting the pressure of a back pressure chamber by a back pressure regulating valve according to the present invention; [Figure 2C] 4 is a diagram illustrating an embodiment of a process of adjusting the pressure of a back pressure chamber by a back pressure regulating valve according to the present invention; [Figure 2D] 4 is a diagram illustrating an embodiment of a process of adjusting the pressure of a back pressure chamber by a back pressure regulating valve according to the present invention; [Figure 2E] 4 is a diagram illustrating an embodiment of a process of adjusting the pressure of a back pressure chamber by a back pressure regulating valve according to the present invention; [Figure 3] 1 is a diagram illustrating an embodiment of a known scroll compressor. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the accompanying drawings, but the embodiments are for a clear understanding of the present invention and the present invention is not limited thereto. In the following description, components having the same reference numerals in different drawings have similar functions, so if it is not necessary for understanding the invention, repeated description will not be made, and known components will be briefly described or omitted, but will not be excluded from the embodiments of the present invention.

[0015] FIG. 1 illustrates an embodiment of a back pressure regulating valve according to the present invention.

[0016] Referring to FIG. 1, the back pressure control valve for an electric scroll compressor includes a first housing 11, a second housing 12, and a communication passage 13 connecting the first and second housings 11, 12; a piston 14 consisting of a first piston 141 located in the first housing 11, a second piston 142 located in the second housing 12, and a piston connecting rod 143 connecting the first and second pistons 141, 142; and the piston 14 is capable of moving up and down inside the first and second housings 11, 12.

[0017] Specifically, pistons 14 are provided inside first and second housings 11 and 12 and move up and down, and pistons 14 are made up of a first piston 141, a second piston 142, and a connecting rod 143 connecting the first and second pistons 141 and 142. The first piston 141 is located inside first housing 11, the second piston 142 is located inside second housing 12, and the piston connecting rod 143 is positioned to pass through the inside of communication passage 13. The first piston 141, the second piston 142, and the piston connecting rod 143 can move up and down inside first housing 11, second housing 12, and communication passage 13, respectively.

[0018] The first housing 11 may be hollow and cylindrical, forming a first receiving space. The second housing 12 may be hollow and cylindrical, forming a second receiving space, and connected to the first housing 11 by a connecting passage 13. The first piston 141 may be cylindrical and housed within the first housing 11, allowing it to move up and down. The second piston 142 may be cylindrical and housed within the second housing 12, allowing it to move up and down, and connected to the first piston 141 by a connecting rod 143. The piston 14 is housed within the valve housing, and the connecting rod 143 moves up and down along the connecting passage 13, allowing the piston 14 to move up and down. The second housing 12 may have a relatively larger cross-sectional area than the first housing 11, and therefore the second piston 142 may have a relatively larger cross-sectional area than the first piston 141; however, the first and second housings 11 and 12 or the first and second pistons 141 and 142 may have various cross-sectional areas and are not limited thereto.

[0019] The back pressure chamber 19 is connected to a third back pressure chamber communicating passage 17 formed in the second housing lower cylinder 121 by a guide path 191. A discharge chamber communicating passage 18 connected to the discharge chamber may be formed on the upper side of the first housing upper cylinder 111. The back pressure chamber communicating passage 15 may include a first back pressure chamber communicating passage 151 formed on a side surface of the first housing 11; a second back pressure chamber communicating passage 152 connected to the first housing lower cylinder 112; and a back pressure chamber connecting passage 153 connecting the first and second back pressure chamber communicating passages 151, 152 with the back pressure chamber 19. In addition, the suction chamber communicating passage 16 may include a first suction chamber communicating passage 161 connected to a side surface of the second housing 12; a first suction chamber communicating passage 162 connected to the second housing upper cylinder 121; and a suction chamber communicating passage 163 connected to the suction chamber. In addition, the discharge chamber communicating passage 18 may be formed in the first housing upper cylinder 111.

[0020] The first piston 141 located within the first housing 11 divides the internal space of the first housing 11 into two spaces, an upper space and an lower space. A first housing upper cylinder 111 may be formed in the space above the first piston 141, and a first housing lower cylinder 112 may be formed in the space below the second piston 142. The second piston 142 located within the second housing 12 divides the internal space of the second housing 12 into two spaces, an upper space and an lower space. Specifically, the internal space of the second housing 12 is divided into a second housing upper cylinder 121 corresponding to the space above the second piston 142, and a second housing lower cylinder 122 corresponding to the space below the second piston 142. The piston 14 can move up and down depending on the magnitude of the force due to the pressure distribution acting on the upper and lower cross-sectional areas of the first piston 141 and the second piston 142. The first housing upper cylinder 111 is constantly supplied with a discharge pressure (P d ) acts on the first housing lower end cylinder 112, and a back pressure (P b ) acts on the second housing upper end cylinder 121. s ) acts on the second housing lower end cylinder 122, and a back pressure (P b The piston 14 moves up and down depending on the operating conditions, i.e., the pressure in the suction or discharge chamber.

[0021] 2A to 2E, first and second elastic units 21 and 22, such as springs, are disposed inside the first housing 11 and the second housing 12. Specifically, the first elastic unit 21 is disposed at the upper end of the first housing 11, and the second elastic unit 22 is disposed at the lower end of the second housing 12, thereby restricting the up and down movement of the first piston 141 and the second piston 142. The movement of the piston 14 determines whether a first back pressure chamber communication passage 151 formed on the side of the first housing 11 is opened or closed depending on the position of the first piston 141. Also, the position of the second piston 142 determines whether a first suction chamber communication passage 161 formed on the side of the second housing 12 is opened or closed depending on the position of the second piston 142. The opening and closing of these communication passages 151 and 161 allows the high pressure (P d) gas flows into the back pressure chamber 19, or the gas in the back pressure chamber 19 flows out to the suction chamber. By controlling the gas inflow and outflow of the back pressure chamber 19 in this way, the pressure in the back pressure chamber 19 can reach a predetermined back pressure value.

[0022] This process will be explained in detail below.

[0023] 2A to 2E illustrate a process in which the pressure in the back pressure chamber is adjusted by the back pressure adjustment valve according to the present invention.

[0024] 2A to 2E, the state depending on the position of the piston

[0025] The position of the piston 14 in the first housing 11 and the second housing 12 corresponds to any one of FIGS. 2A to 2E.

[0026] 2A shows the piston at its highest point, i.e., at top dead center. When the piston reaches top dead center, the first elastic unit 21 is fully compressed, and the second elastic unit 22 is in a free length state, not fully compressed. In this state, the distance between the bottom surface of the second piston 142 and the second elastic unit 22 is at its maximum. In this state, the first back pressure chamber passage 151 is closed, and the first suction chamber communication passage 161 is open.

[0027] 2B, as the first piston 141 moves downward from the top dead center, the contraction displacement of the first elastic unit 21 disappears, and the first elastic unit 21 reaches a free length position. In this state, the first backpressure chamber communicating passage 151 remains closed, and the first suction chamber communicating passage 161 has just been closed. That is, the lower edge of the second piston 142 reaches the lower end of the first suction chamber communicating passage 161, blocking the communicating passage 161.

[0028] 2C, as the second piston 142 moves further downward, the first piston 141 separates from the first elastic unit 21, and the second piston 142 contacts the second elastic unit 22, but the second elastic unit 22 maintains its free length without being compressed. In this state, the first backpressure chamber communicating passage 151 remains closed but is about to be opened, and the first suction chamber communicating passage 161 is in a closed state.

[0029] 2D, the second piston 142 has moved downward to its maximum extent and reached the bottom dead center. At this time, the second elastic unit 22 is fully contracted to its minimum length. In this state, the first backpressure chamber communicating passage 151 is open, and the first suction chamber communicating passage 161 is closed.

[0030] Referring to Figure 2E, this is an intermediate position between the states of Figures 2B and 2C, where the first elastic unit and the second elastic unit 22 are spaced apart from each other, and both the first back pressure chamber connecting passage 151 and the first suction chamber connecting passage 161 are in a closed state.

[0031] In this process, the forces acting on the first and second pistons 141 and 142 are as follows: If the force acting downward on the first piston 141 is F1, the force acting upward on the second piston 142 is F2, and A1, A2, and A0 are the cross-sectional areas of the first piston 141, the second piston 142, and the connecting rod 143, respectively, F1 and F2 can be expressed as the following Equations 1 and 2, respectively.

[0032] F1=A1P d -(A1-A0)P b +k1Δy1(1)

[0033] F2=A2P d -(A2-A0)P s +k2Δy2(2)

[0034] In Equation 1 and Equation 2, k1 and Δy1 are the elastic coefficient and contraction length of the first elastic unit 21 fixed to the upper end surface of the first housing 11, and k2 and Δy2 are the elastic coefficient and contraction length of the second elastic unit 22 fixed to the lower end surface of the second housing 12.

[0035] In Figures 2B, 2C, and 2E, each elastic unit 21, 22 is in a free length state with no displacement, so Δy1 = Δy2 = 0, and therefore F1 and F2 are expressed as the following Equations 3 and 4, respectively.

[0036] F1=A1P d -(A1-A0)P b +k1Δy1(3)

[0037] F2=A2P d -(A2-A0)P s +k2Δy2(4)

[0038] Furthermore, since the force F1 acting on the first piston 141 and the force F2 acting on the second piston 142 are balanced, F1=F2, and the following equation 5 is established.

[0039] A1P d -(A1-A0)P b =A2P b -(A2-A0)P s (5)

[0040] By summarizing Equation 5, Equation 6 is derived.

[0041] A1(P d -P b )=(A2-A0)(P b -P s )(6)

[0042] Back pressure chamber pressure ratio r p If we define it as in Equation 7,

[0043] r p =(P d -P b ) / (P b-P s )(7)

[0044] From Equation 6, the pressure ratio of the back pressure chamber r p is expressed by Equation 8.

[0045] r p =(P d -P b ) / (P b -P s )=(A2-A0) / A1(8)

[0046] In Equation 8, the pressure ratio of the back pressure chamber r p is determined by the cross-sectional area (A1) of the first piston 141, the cross-sectional area (A2) of the second piston 142, and the cross-sectional area (A0) of the connecting rod 143. Therefore, if the cross-sectional areas of the first and second pistons 141 and 142 and the cross-sectional area of ​​the connecting rod 143 are determined, it can be seen from Equation 8 that the pressure ratio becomes a constant. Also, from Equation 8, the back pressure (P b ) is expressed by Equation 9 as follows:

[0047] P b =(P d +r p P s ) / (1+r p )(9)

[0048] The back pressure control valve of the present invention is d ) and suction pressure (P s ) changes, the back pressure in the back pressure chamber is operated to have a value that satisfies Equation 9.

[0049] The piston 14 moves to the position shown in Figure 2B or 2C, or to a position shown in Figure 2E, which is an arbitrary point between Figures 2B and 2C, so that the back pressure reaches a value corresponding to Equation 9. In this position, the first back pressure chamber communication passage 151 and the suction chamber communication passage 161 are closed, and the force F1 acting on the first piston 141 and the force F2 acting on the second piston 142 are balanced.

[0050] The following is a detailed explanation of the piston movement of the back pressure control valve that operates in this manner depending on the change in operating conditions, and the process by which the set back pressure is reached and the piston force is balanced when the set back pressure is reached.

[0051] The change in operating conditions may be an increase or decrease in discharge pressure and an increase or decrease in suction pressure.

[0052] A. Increase in discharge pressure

[0053] The discharge pressure (P d ) increases, the back pressure (P b ) increases as explained below.

[0054] The discharge pressure (P d ) increases, F1 in equation 3 increases and becomes F1>F2, so that the piston 14 moves downward, passing through the position of FIG. 2C and approaching the position of FIG. 2D.

[0055] When the piston 14 descends from the position of FIG. 2C, a reaction force k2Δy2 of the second elastic unit 22 is generated. However, if this reaction force is set to be very small compared to the increase in the gas force (usually, the gas force is very large compared to the reaction forces of the first and second elastic units 21 and 22), the discharge pressure (P d ) increases, F1>F2. That is, d ) increases slightly, F1>F2, and the piston reaches the bottom dead center in Fig. 2D. As soon as the piston passes through Fig. 2C, the gas at discharge pressure filling the first housing upper cylinder 111 flows into the back pressure chamber through the first back pressure chamber communication passage 151, which is opened, and the pressure in the back pressure chamber increases.

[0056] If the pressure in the back-pressure chamber rises, F1 decreases according to Equation 3 and F2 increases according to Equation 2. If, even when the back pressure increases, the state is still such that F1 > F2, the first back-pressure chamber communication passage 151 remains open and the back pressure continues to increase. Eventually, when F2 ≈ F1 or when the force is reversed such that F1 < F2 slightly, at this moment, the piston 14 moves upward and moves until the first back-pressure chamber communication passage 151 closes.

[0057] When the piston 14 is between FIGS. 2C and 2D, an elastic reaction force due to the displacement of the second elastic unit 22 occurs. The role of this half-force is to move the piston 14 upward, that is, to act in the direction of closing the first back-pressure chamber communication passage 151 to restore the force balance when the vertical force balance due to the pressure difference of the pure gas acting on the piston 14 is delicate. The roles of such elastic units 21 and 22 are the same in all the following cases.

[0058] Finally, the piston 14 reaches a new equilibrium, and the back pressure (P b ) becomes the set back-pressure value that satisfies Equation 9 under the new operating conditions. The piston 14 is again between FIGS. 2B and 2C, that is, in a position like FIG. 2E.

[0059] B. Decrease in discharge pressure

[0060] If the discharge pressure (P d ) decreases due to a change in the operating conditions, it can be explained as follows that the back pressure (P b ) decreases according to Equation 9.

[0061] Among the states of FIGS. 2B, 2C, or 2E, which is the state when the piston 14 is in a force balance state, if the discharge pressure (P d ) decreases, F1 decreases and F1 < F2, so the piston 14 moves upward and approaches FIG. 2A through the state like FIG. 2B. When the piston 14 approaches the position of FIG. 2A, the reaction force k1Δy1 of the first elastic unit 21 occurs, but it is set to be very small compared to the increase in the gas force. That is, the discharge pressure (Pd ) Even if it decreases slightly, F1 < F2, and the piston 14 reaches the top dead center of Fig. 2A via Fig. 2B. The backpressure gas filling the lower cylinder 122 of the second housing flows out into the suction chamber through the first suction chamber communication passage 161 that opens from the moment the piston 14 passes through Fig. 2B, and the pressure in the backpressure chamber decreases.

[0062] If the pressure in the backpressure chamber decreases, F1 increases according to Equation 1, and F2 decreases according to Equation 4. Such a decrease in backpressure continues while the first suction chamber communication passage 161 is open, and eventually reaches a moment when F2 ≒ F1 or the force is reversed such that F1 > F2 slightly. At this time, the piston 14 moves downward and moves until the first suction chamber communication passage 161 closes. At this time, the reaction force of the first elastic unit 21 assists the downward movement of the piston 14. At this time, the piston 14 reaches a new equilibrium, and the backpressure (P b ) becomes the set backpressure value that satisfies Equation 9 under the new operating conditions. The piston is again between Fig. 2B and Fig. 2C, that is, in a position like Fig. 2E.

[0063] C. Increased suction pressure

[0064] If the suction pressure (P s ) increases due to a change in the operating conditions, the increase in the backpressure (P b ) according to Equation 9 is explained as follows.

[0065] When the piston 14 is in a state of force equilibrium, if the suction pressure (P s ) increases in any one of the states of Fig. 2B, Fig. 2C or Fig. 2E, F2 decreases according to Equation 4 and F1 > F2, so the piston 14 starts to move downward and approaches the position of Fig. 2D via Fig. 2C. When the piston 14 descends below the position of Fig. 2C, the reaction force k2Δy2 of the second elastic unit 22 is generated.

[0066] When the piston 14 is opened through the first back pressure chamber communication passage 151 that opens from the moment it passes through FIG. 2C, the gas at the discharge pressure filling the upper cylinder 111 of the first housing flows into the back pressure chamber, increasing the pressure in the back pressure chamber.

[0067] When the pressure in the back pressure chamber rises, in Equation 3, F1 decreases, and in Equation 2, F2 increases. Eventually, it reaches a moment when F2≒F1 or the force is reversed slightly such that F1<F2. At this time, the piston 14 moves upward and moves until the first back pressure chamber communication passage 151 closes. At this time, the elastic reaction force of the second elastic unit 22 assists the upward movement of the piston 14.

[0068] Finally, the piston 14 reaches a new equilibrium, and the back pressure (P b ) becomes the set back pressure value that satisfies Equation 9 under the new operating conditions. The piston 14 is again between FIGS. 2B and 2C, that is, in a position like FIG. 2E.

[0069] D. Decreased suction force

[0070] If the suction pressure (P s ) decreases due to a change in the operating conditions, it can be explained as follows that the back pressure (P b ) decreases according to Equation 9.

[0071] If the suction pressure (P s ) decreases in any one of the states of FIGS. 2B, 2C or 2E, which is the state when the piston 14 is in a state of force equilibrium, then in Equation 4, F2 increases and F1<F2, so the piston 14 moves upward and approaches FIG. 2A through the state like FIG. 2B. When the piston 14 approaches the position of FIG. 2A, the reaction force k1Δy1 of the first elastic unit 21 is generated.

[0072] 2B, the backpressure gas filling the second housing lower cylinder 122 flows into the suction chamber through the first suction chamber communication passage 161, which opens, reducing the pressure in the backpressure chamber. As the pressure in the backpressure chamber decreases, F1 increases in Equation 1 and F2 decreases in Equation 4. This reduction in backpressure continues while the first suction chamber communication passage 161 remains open, eventually reaching a point where F2 is approximately equal to F1 or where the forces are slightly reversed, such that F1 > F2. At this point, the piston 14 moves downward until the first suction chamber communication passage 161 closes. At this time, the reaction force of the first elastic unit 21 assists the downward movement of the piston.

[0073] Eventually, the piston 14 reaches a new equilibrium and the back pressure (P b ) becomes the set back pressure value that satisfies Equation 9 under the new operating conditions. The piston 14 is again in a position between FIGS. 2B and 2C, i.e., as shown in FIG. 2E.

[0074] In this way, the back pressure control valve according to the present invention allows the back pressure to always have the value given by Equation 9, regardless of changes in various operating conditions, such as an increase or decrease in the discharge pressure or an increase or decrease in the suction pressure. d ) and suction pressure (P s ) is given, the back pressure (P b ) is the pressure ratio (r p ) is determined by the pressure ratio (r p ) has a fixed value determined by the cross-sectional area (A1) of the first piston 141, the cross-sectional area (A2) of the second piston 142, and the cross-sectional area (A0) of the connecting rod 143, which correspond to the shape and dimensions of the pistons.

[0075] For example, if the diameter of the first piston 141 is 5 mm, the diameter of the second piston 142 is 7.35 mm, and the diameter of the connecting rod 143 is 2 mm, the pressure ratio (r p ) becomes 2.0 and is displayed as Equation 10.

[0076] (P d -P b ) / (Pb -P s )=2.0(10)

[0077] r p = 2.0, the back pressure is expressed as in Equation 11.

[0078] P b =(P d +2P s ) / 3(11)

[0079] The first piston 141, the second piston 142 and the connecting rod 143 may have various dimensions, and the present invention is not limited thereby.

[0080] Although the present invention has been described in detail above with reference to the embodiments presented, those skilled in the art may make various modifications and alterations without departing from the technical spirit of the present invention by referring to the embodiments presented. The present invention is not limited by such modifications and alterations, but is limited only by the scope of the claims. [Industrial Applicability]

[0081] The present invention is applicable to a compressor for a refrigerator in a refrigerated vehicle.

Claims

1. In a back pressure control valve for an electric scroll compressor, a valve housing including a first housing 11, a second housing 12, and a communication passage 13 connecting the first and second housings 11 and 12; a piston 14 including a first piston 141 located in a first housing 11, a second piston 142 located in a second housing 12, and a connecting rod 143 connecting the first and second pistons 141, 142; The piston 14 is movable up and down inside the first and second housings 11 and 12. A back pressure control valve characterized by:

2. The second housing 12 has a relatively large cross-sectional area compared to the first housing 11. The back pressure regulating valve according to claim 1 .

3. The first housing upper cylinder 111 is connected to the discharge chamber, and the first housing lower cylinder 112 is connected to the back pressure chamber. A first back pressure chamber communication passage 151 is formed on the side of the first housing 11, which communicates the first housing upper cylinder 111 with the back pressure chamber 19 when the piston 14 reaches the bottom dead center. The second housing upper cylinder 121 is connected to the suction chamber, and the second housing lower cylinder 122 is connected to the back pressure chamber 19. A first suction chamber communication passage 161 is formed on the side of the second housing 12, which communicates the second housing lower cylinder 122 with the suction chamber when the piston 14 reaches the top dead center. The back pressure regulating valve according to claim 1 .

4. The first housing 11 and the second housing 12 further include elastic units 21 and 22 that are provided in the first housing 11 and the second housing 12 to restrict the movement of the first piston 141 and the second piston 142 and simultaneously provide a restoring force. The back pressure regulating valve according to claim 1 .

5. Pressure ratio r ｐ = (A ２ -A ０ ) / A １ It is displayed in A ０ , A １ and A ２ indicate the cross-sectional areas of the connecting rod 143, the first piston 141, and the second piston 142, respectively. The back pressure regulating valve according to claim 1 .

6. Fixed scrolling and an orbiting scroll that rotates relative to a fixed scroll; a back pressure chamber formed on the back surface of the end plate of the orbiting scroll; The back pressure in the back pressure chamber is formed by the back pressure control valve according to any one of claims 1 to 5. A scroll compressor characterized by:

Images