Back pressure control valve and electric scroll compressor equipped therewith

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 applied to 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 chamber 33 from which compressed refrigerant is discharged; an inlet 34 into which refrigerant flows; a motor 36a for rotating the orbiting scroll 32; and a shaft 36b that rotates the orbiting scroll 32 by the operation of the motor 36a. It may also include a back pressure port 351 or a discharge port 352 for adjusting the pressure between the compression chamber and the back pressure chamber 35, which will be described later. In the case of such an electrically operated scroll compressor, the fixed scroll 31 and fixed scrolling 31A back pressure chamber 35 must be formed on the back of the end plate of the orbiting scroll 32 so as to minimize leakage in the gap between the orbiting scrolls 32 that perform gas compression through orbiting motion in a pair with the fixed scroll 31. Of the gas force formed in the compression chamber, the axial component pushes the orbiting scroll 32 away from the fixed scroll 31, increasing the axial gap between the two scrolls 31 and 32. Therefore, if a back pressure chamber 35 is formed on the back of the end plate of the orbiting scroll 32, the internal pressure of the back pressure chamber 35 generates a back pressure that pushes the orbiting scroll 32 toward the fixed scroll 31, reducing the axial gap. In such a case, if the back pressure is less than the axial gas force, the orbiting scroll 32 will separate from the fixed scroll 31. Conversely, if the back pressure is greater than the axial gas force, the orbiting scroll 32 will be pressed tightly toward the fixed scroll 31. Such tightness generates friction loss between the two scrolls 31 and 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 and 32 while simultaneously preventing friction losses from increasing beyond a predetermined level. A known method for forming the back pressure in the back pressure chamber 35 involves forming a back pressure hole 351 in the end plate of the orbiting scroll to connect the compression chamber on the front of the end plate with the back pressure chamber 35 on the back of the end plate. In this case, gas in the compression chamber flows into the back pressure chamber 35 through the back pressure hole, forming the 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 flowing into the back pressure chamber 35. Although this back pressure hole method is simple in structure, if the operating conditions change, it may not be possible to form an appropriate back pressure corresponding to the operating conditions, resulting in excessive or insufficient back pressure. Another method for forming back pressure in the back pressure chamber is to form the back pressure holes 351 inside the wrap along the corresponding wrap height direction in the axial direction, from the leading edge of the central part of the orbiting scroll wrap to the back surface of the orbiting scroll wrap where the wrap is mounted vertically.In such a case, if the back pressure in the back pressure chamber is sufficient, the tip surface of the orbiting scroll wrap will slide and orbit on the mirror surface of the fixed scroll in a state where it is in close contact with the mirror surface of the fixed scroll and the axial gap is minimized. If the operating conditions change and the back pressure becomes insufficient, the orbiting scroll will be axially separated from the fixed scroll, and such separation creates a gap flow path where the inlet of the back pressure hole formed at the tip surface of the central portion of the orbiting scroll wrap is separated from the mirror surface of the fixed scroll. As a result, the high-pressure gas in the compression chamber located at the central portion flows into the inside of the back pressure hole through the inlet of the back pressure hole thus opened and then into the back pressure chamber. The inflow of such high-pressure gas raises the pressure in the back pressure chamber, making the back pressure in the back pressure chamber larger than the axial gas force and pushing the orbiting scroll upward again toward the fixed scroll side. Different from this, when the operating conditions change such that the discharge pressure decreases or the suction pressure decreases, the excessive back pressure must be appropriately relieved, but there is a drawback in that appropriate back pressure reduction cannot be carried out quickly. In relation to the adjustment of 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 the compression chamber, an outlet that communicates with the back pressure chamber, and a communication hole that communicates the inlet with the inlet. However, the prior art has the aforementioned drawbacks. Therefore, it is necessary to create a method that minimizes the gap between the fixed scroll and the orbiting scroll while quickly responding to changes in operating conditions, and at the same time provides back pressure so that the frictional loss between the orbiting scroll and the fixed scroll does not become excessive. However, the prior art does not disclose such a method.

[0003] The present invention is for solving the problems of the prior art and has the following objectives.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] The object of the present invention is to provide a back pressure control valve capable of providing an optimal value for the back pressure in the back pressure chamber in response to 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 comprising a first housing, a second housing, and a connecting passage between the first and second housings; and a piston comprising 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; the piston being able to move up and down within the first and second housings.

[0007] According to another suitable embodiment of the present invention, the second housing has a relatively larger 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 a discharge chamber, the lower cylinder of the first housing is connected to a back pressure chamber, and a first back pressure chamber communication passage is formed on the side surface of the first housing to connect the upper cylinder of the first housing to the back pressure chamber when the piston reaches bottom dead center, and the upper cylinder of the second housing is connected to an intake chamber, while the lower cylinder of the second housing is connected to a back pressure chamber, and a first intake chamber communication passage is provided on the side surface of the second housing to connect the lower cylinder of the second housing to the intake chamber when the piston reaches top dead center.

[0009] According to yet another suitable embodiment of the present invention, the invention further includes elastic units provided in the first and second housings to restrict the movement of the first and second pistons and to simultaneously provide a restoring force.

[0010] According to yet another suitable embodiment of the present invention, the pressure ratio r pThe result is displayed as =(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, the scroll compressor comprises a fixed scroll; an orbiting scroll that rotates relative to the fixed scroll; a back pressure chamber formed on the back of the end plate of the orbiting scroll; and the back pressure of the back pressure chamber. Adjust A back pressure regulating valve comprising any one of claims 1 to 5; [Effects of the Invention]

[0012] The back pressure control valve according to the present invention provides an optimal back pressure that optimizes the axial adaptation of the orbiting scroll by means of discharge pressure and suction pressure, thereby minimizing leakage and friction losses between the stationary 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 by opening and closing the back pressure passage and suction pressure passage through corresponding up-and-down movement of the piston and the position of the piston 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. The scroll compressor according to the present invention is applied to the compressor of a refrigerator and provides a highly efficient gas compression function with minimized leakage and friction losses. [Brief explanation of the drawing]

[0013] [Figure 1] This is a drawing showing an embodiment of the back pressure control valve according to the present invention. [Figure 2A] This diagram illustrates an embodiment of the process by which the pressure in a back pressure chamber is regulated by the back pressure control valve according to the present invention. [Figure 2B] This diagram illustrates an embodiment of the process by which the pressure in a back pressure chamber is regulated by the back pressure control valve according to the present invention. [Figure 2C] This diagram illustrates an embodiment of the process by which the pressure in a back pressure chamber is regulated by the back pressure control valve according to the present invention. [Figure 2D]This diagram illustrates an embodiment of the process by which the pressure in a back pressure chamber is regulated by the back pressure control valve according to the present invention. [Figure 2E] This diagram illustrates an embodiment of the process by which the pressure in a back pressure chamber is regulated by the back pressure control valve according to the present invention. [Figure 3] This is a drawing showing an embodiment of a known scroll compressor. [Modes for carrying out the invention]

[0014] The present invention will be described in detail below with reference to embodiments shown in the accompanying drawings, but these embodiments are for the purpose of clearly understanding the invention and are not limiting to it. In the following description, components having the same reference numerals in different drawings have similar functions and will not be repeated unless necessary for understanding the invention. Known components will be described briefly or omitted, but will not be excluded from embodiments of the present invention.

[0015] Figure 1 illustrates an embodiment of the back pressure control valve according to the present invention.

[0016] Referring to Figure 1, the back pressure control valve for the electric scroll compressor includes a first housing 11, a second housing 12, and a connecting passage 13 that connects the first and second housings 11 and 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 that connects the first and second pistons 141 and 142; the piston 14 is vertically movable within the first and second housings 11 and 12.

[0017] Specifically, pistons 14 are provided inside the first and second housings 11 and 12 to perform up-and-down motion. The pistons 14 consist of a first piston 141, a second piston 142, and a connecting rod 143 that connects the first and second pistons 141 and 142. The first piston 141 is located inside the first housing 11, the second piston 142 is located inside the second housing 12, and the piston connecting rod 143 is located in a manner that penetrates the inside of the connecting passage 13. The first piston 141, the second piston 142, and the piston connecting rod 143 are capable of up-and-down motion inside the first housing 11, the second housing 12, and the connecting passage 13, respectively.

[0018] The first housing 11 can be hollow and cylindrical, forming a first housing space. The second housing 12 can be hollow and cylindrical, forming a second housing space, and is connected to the first housing 11 by a connecting passage 13. The first piston 141 can be cylindrical, housed inside the first housing 11, and have a structure that allows it to move up and down. The second piston 142 can be cylindrical, housed inside the second housing 12, and have a structure that allows it to move up and down, and is connected to the first piston 141 by a connecting rod 143. The piston 14 is housed inside the valve housing, and the piston 14 can move up and down as the connecting rod 143 moves up and down along the connecting passage 13. The second housing 12 can have a relatively larger cross-sectional area than the first housing 11, and as a result, the second piston 142 can 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, can have a variety of cross-sectional areas and are not limited thereto.

[0019] The back pressure chamber 19 is connected to the second housing by the guideway 191. Lower cylinder 122 It is connected to the third back pressure chamber connecting passage 17 formed therein. top end A discharge chamber connecting passage 18 may be formed on the upper side of the cylinder 111, which is connected to the discharge chamber. The back pressure chamber connecting passage 15 is a first back pressure chamber connecting passage 151 formed on the side of the first housing 11; first housing lower endThe second back pressure chamber connecting passage 152 connected to the cylinder 112; and the back pressure chamber connecting passage 153 connecting the first and second back pressure chamber connecting passages 151 and 152 to the back pressure chamber 19; may also consist of the first inhalation chamber connecting passage 161 connected to the side of the second housing 12; and the second housing top end Connected to cylinder 121 2nd It may consist of an inhalation chamber connecting passage 162 and an inhalation chamber connecting passage 163 connected to the inhalation chamber. Also, the first housing top end A discharge chamber connecting passage 18 can be formed in the 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, vertically. The upper space above the first piston 141 contains the first housing upper cylinder 111 and Chapter 1, 141 A first housing lower end cylinder 112 may be formed in the lower space of the first housing 141. The internal space of the second housing 12 is divided into two spaces vertically by a second piston 142 located inside the second housing 12. Specifically, the internal space of the second housing 12 is divided into a second housing upper end cylinder 121, which corresponds to the upper space of the second piston 142, and a second housing lower end cylinder 122, which corresponds to the lower space of the second piston 142. The piston 14 can move up and down depending on the magnitude of the force due to the pressure distribution on the upper and lower cross-sectional areas of the first piston 141 and the second piston 142. The first housing upper end cylinder 111 is always subjected to a discharge pressure (P d ) acts, and a constant back pressure (P b ) acts upon the lower end suction pressure (P s ) acts, and a constant back pressure (P b The piston 14 moves up and down due to changes in operating conditions, i.e., the pressure in the intake chamber or discharge chamber.

[0021] Referring to Figures 2A to 2E, spring-like first and second elastic units 21 and 22 are arranged inside the first housing 11 and the second housing 12. Specifically, the first elastic unit 21 is provided at the upper end of the first housing 11, and the second elastic unit 22 is provided 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 these pistons 14 determines the opening and closing of the first back pressure chamber communication passage 151 formed on the side surface of the first housing 11, depending on the position of the first piston 141. Similarly, the opening and closing of the first intake chamber communication passage 161 formed on the side surface of the second housing 12 is determined by the position of the second piston 142. High pressure (P) is released through the opening and closing of these communication passages 151 and 161. d The gas from the back pressure chamber 19 flows into the back pressure chamber 19, or the gas from the back pressure chamber 19 flows out into the suction chamber. Through this control of the gas inflow and outflow of the back pressure chamber 19, the pressure in the back pressure chamber 19 can reach a predetermined back pressure value.

[0022] The following will provide a detailed explanation of this process.

[0023] Figures 2A to 2E illustrate the process by which the pressure in the back pressure chamber is regulated by the back pressure control valve according to the present invention.

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

[0025] The position of the piston 14 within the first housing 11 and the second housing 12 corresponds to one of the positions shown in Figures 2A to 2E.

[0026] Figure 2A shows the piston at its highest position, i.e., at top dead center. Upon reaching top dead center, the first elastic unit 21 is fully contracted, and the second elastic unit 22 is in a free length state, not contracted at all. In this state, the separation distance between the lower end 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 intake chamber connecting passage 161 is open.

[0027] Referring to Figure 2B, as the first piston 141 moves downward from top dead center, the contraction displacement of the first elastic unit 21 disappears, and this is the position where the first elastic unit 21 is at its free length. In this state, the first back pressure chamber communication passage 151 continues Close As a result, the first inhalation chamber passage 161 is just closed. That is, the lower end edge of the second piston 142 reaches the lower end of the first inhalation chamber passage 161 and blocks the passage 161.

[0028] Referring to Figure 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 comes into contact with the second elastic unit 22, but the second elastic unit 22 is still in a state where it has not yet contracted and is at its free length. In this state, the first back pressure chamber communication passage 151 continues Close However, it is about to open, and the first inhalation chamber connecting passage 161 is closed.

[0029] Referring to Figure 2D, the second piston 142 has moved to its maximum downward position and reached bottom dead center. At this time, the second elastic unit 22 is contracted to its minimum length. In this state, the first back pressure chamber communication passage 151 is open, and the first intake chamber communication passage 161 is closed.

[0030] Referring to Figure 2E, this is an intermediate position between the states in Figure 2B and Figure 2C, separated from both sides of the first elastic unit and the second elastic unit 22, and both the first back pressure chamber communication passage 151 and the first suction chamber communication passage 161 are closed.

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

[0032] F1 = A1P d -(A1 - A0)P b + k1Δy1(1)

[0033] F2 = A2 P b -(A2 - A0)P s + k2Δy2(2)

[0034] In Equations (1) and (2), k1 and Δy1 are the elastic coefficient and the 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 the contraction length of the second elastic unit 22 fixed to the lower end surface of the second housing 12.

[0035] In FIGS. 2B, 2C, and 2E, since each of the elastic units 21 and 22 is in a free length state without displacement, Δy1 = Δy2 = 0, and thus, F1 and F2 are expressed as the following Equations (3) and (4), respectively.

[0036] F1 = A1P d -(A1 - A0)P b ( 3)

[0037] F2 = A2 P b -(A2 - A0)P s ( 4)

[0038] Further, since the force F1 acting on the first piston 141 and the force F2 acting on the second piston 142 are in equilibrium, F1 = F2, and the following Equation (5) is established.

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

[0040] When Equation (5) is summarized, Equation (6) is derived.

[0041] A1(P d - Pb )=(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 r of the back pressure chamber p This 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 r of the back pressure chamber p This 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. Thus, once the cross-sectional areas of the first and second pistons 141 and 142 and the connecting rod 143 are determined, the pressure ratio can be seen from Equation 8 as a constant. Furthermore, from Equation 8, the back pressure (P) can be calculated. b ) is expressed in Equation 9 as shown below.

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

[0048] The back pressure control valve of the present invention controls the discharge pressure (P) which is an operating condition. d ) and suction pressure (P s When the value changes, the back pressure chamber operates so that the back pressure satisfies equation 9.

[0049] The piston 14 moves so that the back pressure reaches the value corresponding to Equation 9, and is placed in the position shown in Figure 2B or Figure 2C, or any point between Figures 2B and 2C, such as in Figure 2E. 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 in equilibrium.

[0050] Next is a detailed explanation of the piston movement of the back pressure control valve in response to changes in operating conditions, how it reaches the set back pressure, and the process by which the piston force becomes balanced when the set back pressure is reached.

[0051] Changes in operating conditions may include an increase or decrease in discharge pressure, and an increase or decrease in suction pressure.

[0052] A. Increase in discharge pressure

[0053] Discharge pressure (P) changes depending on operating conditions d If the ) increases, the back pressure (P) will increase according to Equation 9. b ) increases as explained below.

[0054] In any one of the states shown in Figures 2B, 2C, or 2E, which represent the state when the piston 14 is in a state of force equilibrium, the discharge pressure (P d If ) increases, F1 in equation 3 increases to F1 > F2, so the piston 14 moves downward, passing through the position in Figure 2C and approaching the position in Figure 2D.

[0055] When the piston 14 descends below the position shown in Figure 2C, a reaction force k2Δy2 is generated in the second elastic unit 22. However, if this is set to be very small compared to the increase in 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 As the discharge pressure (P) increases, F1 > F2. d) Even if it increases slightly, F1 > F2, and the piston reaches the bottom dead center in Fig. 2D. The gas at the discharge pressure that fills the upper cylinder 111 of the first housing through the first back pressure chamber communication passage 151 that opens from the moment the piston passes through Fig. 2C flows into the back pressure chamber, increasing the pressure in the back pressure chamber.

[0056] If the pressure in the back pressure chamber increases, F1 decreases according to Equation 3, and F2 increases according to Equation 2. If, even when the back pressure increases, the state is still F1 > F2, the first back pressure chamber communication passage 151 remains open and the back pressure continues to increase. 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 until the first back pressure chamber communication passage 151 closes.

[0057] When the piston 14 is between Fig. 2C and Fig. 2D, an elastic reaction force due to the displacement of the second elastic unit 22 occurs. reaction force Its role is to move the piston 14 upward when the balance of the up and down forces due to the pressure difference of the pure gas acting on the piston 14 is delicate, that is, it acts in the direction of closing the first back pressure chamber communication passage 151 to help restore the force balance. 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 returns to a position between Fig. 2B and Fig. 2C again, that is, 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] Of the states shown in FIGS. 2B, 2C, or 2E when the piston 14 is in a state of force balance, 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 as shown in FIG. 2B. When the piston 14 approaches the position of FIG. 2A, the reaction force k1Δy1 of the first elastic unit 21 is generated, but it is set to be very small compared to the increase in gas force. That is, even if the discharge pressure (P d ) decreases slightly, F1 < F2, and the piston 14 reaches the top dead center of FIG. 2A through 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 returns to a position between FIG. 2B and FIG. 2C again, that is, a position like FIG. 2E.

[0063] C. Increased intake pressure

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

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

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

[0067] If the pressure in the back pressure chamber increases, F1 decreases in Equation 3 and F2 increases in Equation 2. 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 Fig. 2B and Fig. 2C, that is, in a position like Fig. 2E.

[0069] D. Decrease in suction power

[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 Fig. 2B, Fig. 2C or Fig. 2E, which is the state when the piston 14 is in a state of force equilibrium, F2 increases in Equation 4 and F1 < F2, so the piston 14 moves upward and approaches Fig. 2A through a state like Fig. 2B. When the piston 14 approaches the position in Fig. 2A, the reaction force k1Δy1 of the first elastic unit 21 occurs.

[0072] As piston 14 passes through Figure 2B, the back pressure gas filling the second housing lower end cylinder 122 flows out into the intake chamber through the first intake chamber communication passage 161, which opens, causing the pressure in the back pressure chamber to decrease. As the pressure in the back pressure chamber decreases, F1 increases in Equation 1 and F2 decreases in Equation 4. This decrease in back pressure persists while the first intake chamber communication passage 161 is open, eventually reaching a point where F2 ≈ F1, or a slight reversal of forces where F1 > F2. At this point, piston 14 moves downward until the first intake chamber communication passage 161 closes. During this process, the reaction force of the first elastic unit 21 assists the downward movement of the piston.

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

[0074] Thus, the back pressure control valve according to the present invention ensures that the back pressure always maintains a value given by Equation 9, regardless of various changes in operating conditions such as an increase or decrease in discharge pressure or an increase or decrease in suction pressure. In Equation 9, the discharge pressure (P d ) and suction pressure (P s When ) is given, back pressure (P b ) is the pressure ratio (r p It is determined by ). By the way, the pressure ratio (r) defined in Equation 8 p 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 have a fixed value that corresponds to the shape dimensions of the piston.

[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, then the pressure ratio (r p ) becomes 2.0 and is displayed as in Equation 10.

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

[0077] r p When the value is 2.0, the back pressure is expressed as shown 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 can have a variety of dimensions, and this does not limit the present invention.

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

[0081] This invention is applicable as a compressor for the refrigeration system of a refrigerated vehicle.

Claims

1. In a back pressure control valve for an electric scroll compressor, A valve housing comprising a first housing (11), a second housing (12), and a connecting passage (13) between the first housing (11) and the second housing (12), A piston (14) comprising a first piston (141) located in the first housing (11), a second piston (142) located in the second housing (12), and a connecting rod (143) that connects the first piston (141) and the second piston (142) and is positioned to penetrate the interior of the communication passage (13); The piston (14) is able to move up and down inside the first housing (11) and the second housing (12), The second housing (12) has a relatively larger cross-sectional area compared to the first housing (11). In the internal space of the first housing (11), the upper cylinder (111), which is the upper space of the first piston (141), is connected to the discharge chamber, and the lower cylinder (112), which is the lower space of the first piston (141), is connected to the back pressure chamber (19). A first back pressure chamber connecting passage (151) is formed on the side surface of the first housing (11), and when the piston (14) reaches the bottom dead center, the upper cylinder (111) of the first housing and the back pressure chamber (19) are connected. In the internal space of the second housing (12), the upper cylinder (121) of the second housing, which is the upper space of the second piston (142), is connected to the intake chamber, and the lower cylinder (122) of the second housing, which is the lower space of the second piston (142), is connected to the back pressure chamber (19). A first intake chamber communication passage (161) is formed on the side surface of the second housing (12), and when the piston (14) reaches top dead center, the lower cylinder (122) of the second housing and the intake chamber are connected. A back pressure control valve characterized by the following features.

2. Further comprising elastic units (21, 22) 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 to simultaneously provide a restoring force The back pressure control valve according to claim 1.

3. r ｐ = (A ２ -A ０ ) / A １ It is displayed in A ０ A １ and A ２ The pressure ratio (rp) representing the cross-sectional area of ​​the connecting rod (143), the first piston (141), and the second piston (142), respectively, is used to respond to changes in operating conditions. Pb = (Pd + rp Ps) / (1 + rp), where Pd and Ps determine the back pressure (Pb) which represents the discharge pressure and suction pressure, respectively. The back pressure control valve according to claim 1.

4. Fixed scrolling and, A rotating scroll relative to the fixed scroll, The back pressure chamber (19) formed on the back surface of the end plate of the orbiting scroll, Includes a back pressure regulating valve according to any one of claims 1 to 3, which adjusts the back pressure of the back pressure chamber (19) A scroll compressor characterized by the following features.

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