Back pressure regulating valve and an electric type of a scroll compressor with the same

Abstract

Provided is a back pressure regulating valve and an electric type of a scroll compressor with the same. A valve of an electric scroll compressor for regulating a back pressure includes a valve housing including a first housing 11, a second housing and a communicating passage 13 for connecting the first housing 11 to the second housing 12; and a piston 14 including a first piston 141 located within the first housing 11, a second piston located within the second housing 12 and a connecting rod 143 for connecting the first piston 141 to the second piston 142, wherein the piston 14 is configured to move up and down within the first and the second housing 11, 12.

Claims

1. A valve of an electric scroll compressor for regulating a back pressure, comprising: a valve housing including a first housing, a second housing and a communicating passage for connecting the first housing to the second housing; and a piston including a first piston located within the first housing, a second piston located within the second housing and a connecting rod for connecting the first piston to the second piston, wherein the piston is configured to move up and down within the first and the second housing, wherein the cross sectional size of the second housing is bigger than that of the first housing, and wherein a first housing upper cylinder is connected to a discharging chamber, a first housing lower cylinder is connected to a back pressure chamber, a first back pressure chamber communicating passage is formed at a side of the first housing for the first housing upper cylinder to communicate with a back pressure chamber when the piston reaches at a bottom dead center, a second upper cylinder is connected to a suction chamber and a second lower cylinder is connected to the back pressure chamber, and a first suction chamber communicating passage is formed at a side of the second housing for the second housing lower cylinder to communicate with the suction chamber when the piston reaches at a top dead center.

2. The valve according to claim 1, further comprising elastic units installed at the first housing and the second housing for limiting a movement of the first piston and the second piston and at the same time for supplying a restoring force.

3. The valve according to claim 1, wherein a pressure ratio is represented as rp=(A2A0)/A1, wherein A0, A1 and A2 are cross sectional sizes of the connecting rod, the first piston and the second piston, respectively.

4. A scroll compressor, comprising: a fixed scroll; an orbiting scroll for orbiting around the fixed scroll; a back pressure chamber formed at a rear surface of a head plate of the orbiting scroll; and a valve for regulating a back pressure according to claim 1.

5. A scroll compressor, comprising: a fixed scroll; an orbiting scroll for orbiting around the fixed scroll; a back pressure chamber formed at a rear surface of a head plate of the orbiting scroll; and a valve for regulating a back pressure according to claim 2.

6. A scroll compressor, comprising: a fixed scroll; an orbiting scroll for orbiting around the fixed scroll; a back pressure chamber formed at a rear surface of a head plate of the orbiting scroll; and a valve for regulating a back pressure according to claim 3.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows an embodiment of a valve for regulating a back pressure according to the present invention.

(2) FIG. 2A to 2E shows an embodiment of a process for regulating a back pressure by the valve for regulating the back pressure according to the present invention.

(3) FIG. 3 shows an embodiment of a known scroll compressor.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

(4) Exemplary embodiments of the present invention will be described herein below with reference to the accompanying drawings.

(5) FIG. 1 shows an embodiment of a valve for regulating a back pressure according to the present invention.

(6) Referring to FIG. 1, a valve of an electric scroll compressor for regulating a back pressure comprises a valve housing including a first housing 11, a second housing 12 and a communicating passage 13 for connecting the first housing 11 to the second housing 12; and a piston 14 including a first piston 141 located within the first housing 11, a second piston 142 located within the second housing 12 and a connecting rod 143 for connecting the first piston 141 to the second piston 142, wherein the piston 14 is configured move up and down within the first and the second housings 11, 12.

(7) Specifically, the piston 14 is installed within the first and the second housings 11, 12 to move up and down, and comprises the first piston 141; the second piston 142; and the connecting rod 143 for connecting the first piston 141 to the second piston 142. The first piston 141 is located within the first housing 11; the second piston 142 is located within the second housing 12; and the piston connecting rod 143 is located in a way to penetrate the communicating passage 13. The first piston 141, the second piston 142 and the connecting rod 143 can move up and down within the first housing 11, the second housing 12 and the communicating passage 13, respectively. The first housing 11 may be a hollow cylindrical shape, and form a first receiving volume. The second housing 12 may be a hollow cylindrical shape to form a second receiving volume, and the second housing 12 may be connected to the first housing by the communicating passage 13. The first piston 141 may be a cylindrical shape to be received within the first housing 11, and the first piston 141 may move up and down within the first housing 11. The second piston 142 may be a cylindrical shape to be received within the second housing 12 for moving up and down within the second housing 12, and the second piston 142 may be connected to the first piston 141 by the connecting rod 143. The piston 14 may be received within the valve housing, and the connecting rod 143 moves up and down along the communicating passage 13, thereby the piston 14 may move up and down. The cross sectional size of the second housing 12 may be bigger than that of the first housing 11, thereby the cross sectional size of the second piston 142 may be bigger than that of the first piston 141, but the first or second housing 11, 12 or the first or second piston 141, 142 may have various cross sectional sizes, but not limited to.

(8) The first piston 141 located within the first housing 11 may divide an inner volume of the first house 11 into two partial volumes along up and down direction. The first upper cylinder 111 may be formed at the upper volume of the first piston 141, and the first lower cylinder 112 may be formed at the lower volume of the second piston 14, respectively. The second piston 142 may divide an inner volume of the second housing 12 into two partial volumes along up and down direction. Specifically, the inner volume of the second housing 12 may be divided into the second upper cylinder 121 corresponding to an upper volume of the second piston 14 and the second housing lower cylinder 122 corresponding to a lower volume of the second piston 142, respectively. The piston 14 may move up and down depending on the force size according to a pressure distribution applied to up and down cross section of the first piston 141 and the second piston 141. A discharging pressure Pd may be always applied to the first housing upper cylinder 111, and a back pressure Pb may be always applied to the first housing lower cylinder 112. And a lower suction pressure Ps may be applied to the second housing upper cylinder 121, and the back pressure Pb may be applied to the second housing lower cylinder 122. The piston 14 moves up and down according to a change of a running condition, that is, the pressure of the suction chamber or the discharging chamber.

(9) FIG. 2A to 2E shows an embodiment of a process for regulating a back pressure by the valve for regulating the back pressure according to the present invention.

(10) Referring to FIG. 2A to FIG. 2E, a first and second elastic units 21, 22 such as a spring may be placed with the first housing 11 and the second housing 12. Specifically, the first elastic unit 21 may be placed at an upper part of the first housing 11, and the second elastic unit 22 may be placed at a lower part of the second housing 12, and thereby, the up and down movement of the first piston 141 and the second piston 142 may be restricted. An opening and closing of the first back pressure communicating passage 151 formed at a side part of the first housing 11 may be determined according to the position of the first piston 141 depending on the movement of the piston 14. And also, an opening and closing of the first suction chamber communicating passage 161 formed at the side part of the second housing 12 may be determined according to the position of the second piston 141. A gas with a high pressure of Pd may enter the back pressure chamber 19, or the gas of the back pressure chamber 19 may be discharged to the suction chamber through the opening and closing of the communicating passage 151, 161. The pressure of the back pressure chamber 19 may reach a predetermined back pressure value by controlling such a gas entering and discharging of the back pressure chamber 19.

(11) Such process will be discussed in the following.

(12) A Condition According to the Position of the Piston in FIG. 2A to FIG. 2E

(13) The positon of the piston 14 within the first housing 11 and the second housing 12 corresponds to any one among FIG. 2A to FIG. 2E.

(14) FIG. 2A shows a condition that the piston 14 is located at the highest position, that is, reaches the top dead center. When the piston 14 reaches the top dead center, the first elastic unit 21 may be contracted maximally, and the second elastic unit 22 becomes a free length state in which it is not contracted at all. In this condition, the separating distance between the lower surface of the second piston 142 and the second elastic unit 22 becomes maximum. And, in this condition, the first back pressure chamber communicating passage 151 is closed and the first suction chamber communicating passage 161 is in an open state.

(15) Referring FIG. 2B, the first piston 141 moves downward from the top dead enter to make the contracted displacement of the first elastic unit 21 disappear gradually, and thereby, the first elastic unit 21 becomes in a free length state. In this condition, the first back pressure chamber communicating passage 151 remains in a closed state, and the first suction chamber communicating chamber 161 is just closed. That is, the lower corner of the second piston 142 reaches the lower end of the first suction chamber communicating passage 161 to block the communicating passage 161.

(16) Referring to FIG. 2C, if the second piston 142 further moves downwardly, then the first piston 141 is separated from the elastic unit 21, and the second piston 142 contacts the second elastic unit 22 to remain in a free length state and to perform no contraction. In this condition, the first back pressure chamber communicating passage 151 remains in a closed state and is about to be opened, and the first suction chamber communicating passage 161 is in a closed state.

(17) Referring to FIG. 2D, the second piston 142 moves downwardly as much as possible to reach the bottom dead center. In such condition, the second elastic unit 22 contracts maximally to become a minimum length. In this condition, the first back pressure chamber communicating passage 151 remains in an open state, and the first suction chamber communicating passage 161 remains in a closed state.

(18) Referring to FIG. 2E, the depicted example shows a middle state of the example of FIG. 2B and FIG. 2C, the piston 14 is separated from both of the first elastic unit 21 and the second elastic unit 22, and both of the first back pressure chamber communicating passage 151 and the first suction chamber communicating passage 161 are in a closed state.

(19) In this course, the forces acting on the first and second piston 141, 142 are as follows. If F1 is a force acting downward on the first piston 141, F2 is a force acting upward on the second piston 142, A1, A2 and A0 become the cross section size of the first, second piston 141, 142 and the connecting rod 143, respectively, then F1 and F2 are expressed as equations (1) and (2) below.

(20) $\begin{array}{cc}{F}_1=A_1{P}_d-\left(A_1-A_0\right)P_b+k_1{y}_1& \left(1\right)\end{array}$$\begin{array}{cc}{F}_2=A_2{P}_b-\left(A_2-A_0\right)P_s+k_2{y}_2.& \left(2\right)\end{array}$

(21) In equation (1) and (2), k1 and y1 are the elastic coefficient and the contracted length of the first elastic unit 21 fixed at the upper surface of the first housing 11, and k2 and y2 are the elastic coefficient and the contracted length of the second elastic unit 22 fixed at the lower surface of the second housing 12.

(22) In FIGS. 2B, 2C and 2E, each elastic unit 21, 22 is in a free length state having no displacement, therefore y1=y2-0, and thereby, F1 and F2 may be expressed as equations (3) and (4) below.

(23) $\begin{array}{cc}{F}_1=A_1{P}_d-\left(A_1-A_0\right)P_b& \left(3\right)\end{array}$$\begin{array}{cc}{F}_2=A_2{P}_b-\left(A_2-A_0\right)P_s& \left(4\right)\end{array}$

(24) And also, force F1 acting on the first piston 141 and force F2 acting on the second piston F2 is in an equilibrium state to be expressed as F1=F2, and the following equation (5) is established.

(25) $\begin{array}{cc}{A}_1{P}_d-\left(A_1-A_0\right)P_b=A_2{P}_b-\left(A_2-A_0\right)P_s& \left(5\right)\end{array}$

(26) If equation (5) is rearranged, then equation (6) below is derived.

(27) $\begin{array}{cc}{A}_1\left(P_d-P_b\right)=\left(A_2-A_o\right)\left(P_b-P_s\right)& \left(6\right)\end{array}$

(28) If the back pressure chamber pressure ratio rp is defined as equation (7) below,

(29) $\begin{array}{cc}{r}_p=\frac{P_d-P_b}{P_b-P_s}& \left(7\right)\end{array}$

(30) The back pressure chamber pressure ratio rp is expressed as following equation (8) from equation (6).

(31) $\begin{array}{cc}{r}_p=\frac{P_d-P_b}{P_b-P_s}=\frac{A_2-A_0}{A_1}& \left(8\right)\end{array}$

(32) In equation (8), the back pressure chamber pressure ratio rp is determined by the cross sectional size A1 of the first piston 141, the cross sectional size A2 of the second piston 142 and the cross sectional size A0 of the connecting rod 143. Therefore, if the cross sectional size of the first and second piston 141, 142 and the connecting rod 143 are determined, the pressure ratio becomes a constant value from the equation (8) above.

(33) And also, the back pressure (Pb) may be expressed as the following equation (9).

(34) $\begin{array}{cc}{P}_b=\frac{P_d+r_p{P}_s}{1+r_p}& \left(9\right)\end{array}$

(35) The back pressure regulating valve according to the present invention operates in a way that the back pressure of the back pressure chamber has a value to satisfy the equation (9) when the discharging pressure Pd and the suction pressure Ps corresponding to the running condition changes.

(36) The piston 14 moves in a way that the back pressure reaches a value corresponding to the equation (9), and then the piston 14 may be placed at the position shown in FIG. 2B or in FIG. 2C, or may be placed at a position shown in FIG. 2E corresponding to any position located between the positions shown in FIG. 2B and in FIG. 2C. At this position, the first back pressure chamber communicating passage 151 and the suction chamber communicating passage 161 is in a closed stage, and the force F1 acting on the first piston 141 and the force F2 acting on the second piston 142 are in an equilibrium condition.

(37) The following is a detailed description of the piston motion of the back pressure regulating valve operating together according to the change of the running condition and a process of reaching a predetermined back pressure and of achieving an equilibrium condition on reaching the predetermined back pressure.

(38) The change of the running condition may comprise an increase or a decrease of the discharging pressure; and an increase or a decrease of suction pressure.

(39) A. Discharging Pressure Increase

(40) If the discharging pressure Pd increases because of the change of the running condition, then the back pressure Pb increases according to the equation (9) as in the following description.

(41) If the discharging pressure Pb increases in any state out of the states shown in FIG. 2B, 2C or 2E corresponding to a force equilibrium state of the piston 14, then F1 increases in the equation (3) to become F1>F2. Accordingly, the piston 14 moves downward to approach to a position shown in FIG. 2D after passing a positon shown in FIG. 2C. If the piston 14 moves below the positon shown in FIG. 2C, then a reacting force k2y2 of the second elastic unit 22 may be generated. But if the reacting force is set as much smaller than the gas force increment (the gas force generally is much greater than the reacting force of the first and second elastic unit 21, 22), then F1>F2 finally owing to the increase of the discharging pressure Pd. That is, even though the discharge pressure increases a little, F1>F2 and the piston may reach the bottom dead center shown in FIG. 2d. The first back pressure chamber communicating passage 151 is opened at the moment when the piston passes the position shown in FIG. 2C, and the discharging pressure gas filled in the first housing upper cylinder 111 enters the back pressure chamber through the first back pressure chamber communicating passage 151 to increase the pressure of the pack pressure chamber.

(42) If the pressure of the back pressure chamber increases, then F1 decreases in the equation (3) and F2 increases in the equation (2). Even though the back pressure increases in a state of F1>F2, the first back pressure chamber communicating passage 151 remains in an open state continuously to increase the back pressure continuously. Finally, the condition reaches a state that F2 is nearly equal to F1 or the moment when F1<F2 by a narrow margin for reversing from a state of F1>F2, and at this moment, the piston 14 moves upward until the first back pressure chamber communicating passage 151 is closed.

(43) When the piston 14 is placed in a position between the positions shown in FIG. 2C and FIG. 2D, an elastic reaction force by a displacement of the second elastic unit 22 may be generated. The role of the reaction force is to move the piston upwardly when the force equilibrium in up and down direction by the pressure difference of a pure gas acting on the piston 14 is minute. That is, the reaction force helps to restore the force equilibrium by acting in a direction to close the first back pressure chamber communicating passage 151. The role of the first and second elastic unit 21, 22 may be identical to all the following cases.

(44) Finally, the piston 14 reaches a new equilibrium state, and the back pressure Pb becomes a predetermined back pressure value satisfying the equation (9) in a new running condition. The piston 14 is placed at a position between the positions shown in FIGS. 2B and 2C, that is, a position such as the positon shown in FIG. 2E.

(45) B. Discharging Pressure Decrease

(46) If discharging pressure Pd decreases because of the change of the running condition, then the back pressure Pb decreases according to the equation (9) as discussed in the following.

(47) If the discharging pressure Pd decreases in a state that the piston 14 is placed at a positon among the positions shown in FIG. 2B, 2C or 2E corresponding to a force equilibrium state, then F1 decreases to become F1<F2. Accordingly, the piston 14 moves upward to approach to the position shown in FIG. 2A via the position shown in FIG. 2B. If the piston 14 approaches to the position shown in FIG. 2A, then a reaction force k1y1 of the first elastic unit 21 may be generated. However, the reaction force is set as little as possible compared with the increment of the gas force. That is, if the discharging pressure Pd decreases by a minute amount, then the state becomes F1>F2 and the piston 14 reaches the bottom dead center shown in FIG. 2A via the positon shown in FIG. 2B. The back pressure gas filled in the second housing lower cylinder 122 flows to the suction chamber through the first suction chamber communicating passage 161 which is opened at the moment when the piston 14 passes the position shown in FIG. 2B, and the pressure of the back pressure chamber decreases. If the pressure of the back pressure chamber decreases, then F1 increases in the equation (1), and F2 decreases in the equation (4). Such decrease of the back pressure continues till the first suction chamber communicating passage 161 is in an open state, finally F2 is nearly equal to F1 or a moment when the force is reversed as F1>F2 by a narrow margin arrives, and at this time, the piston 14 moves downward continuously till the first suction chamber communicating passage 161 is closed. In this time, the reaction force of the first elastic unit 21 helps the piston 14 to move downward. In this condition, the piston 14 reaches a new equilibrium state, and the back pressure Pb becomes a new set back pressure value satisfying the equation (9) in a new running condition. The piston 14 is placed again at the positon between positions shown in FIGS. 2B and 2C, that is, the position shown in FIG. 2E.

(48) C. Suction Pressure Increase

(49) If the suction pressure Ps increases because of the change of the running condition, then the back pressure Pb increases according to the equation (9) as discussed in the following.

(50) If the suction pressure Ps increases in a state that the piston 14 is placed at a positon among the positions shown in FIG. 2B, 2C or 2E corresponding to a force equilibrium state, then F2 in the equation (4) decreases to become F1>F2. Accordingly, the piston 14 moves downward to approach to the position shown in FIG. 2D via the position shown in FIG. 2C. If the piston 14 moves to a lower positon than the position shown in FIG. 2C, a reaction force k2y2 of the second elastic unit 22 may be generated.

(51) The discharging pressure gas filled in the first housing upper cylinder 111 enter the back pressure chamber through the first back pressure chamber communicating passage 151 which starts to open at the moment when the piston 14 passes the positon shown in FIG. 2C, and the pressure of the back pressure chamber increases.

(52) If the pressure of the back pressure chamber increases, then F1 decreases in the equation (3), and F2 increases in the equation (2). Finally, F2 is nearly equal to F1 or a moment when the force is reversed as F1<F2 minutely arrives, and at this time, the piston 14 moves upward continuously till the first back pressure chamber communicating passage 151 is closed. In this time, the reaction force of the second elastic unit 22 helps the piston 14 to move upward.

(53) Finally, the piston 14 reaches a new equilibrium state, and the back pressure Pb becomes a new set back pressure value satisfying the equation (9) in a new running condition. The piston 14 is placed again at the positon between positions shown in FIGS. 2B and 2C, that is, the position shown in FIG. 2E.

(54) D. Suction Pressure Decrease

(55) If the suction pressure Ps decreases because of the change of the running condition, then the back pressure decreases according to the equation (9) as discussed in the following.

(56) If the discharging pressure Ps decreases in a state that the piston 14 is placed at the positon out of the positions shown in FIG. 2B, 2C or 2E corresponding to a force equilibrium state, then F2 increases to become F1<F2. Accordingly, the piston 14 moves upward to approach to a position shown in FIG. 2A via the position shown in FIG. 2B. If the piston approaches to the positon shown in FIG. 2C, a reaction force k1y1 of the first elastic unit 21 may be generated.

(57) The back pressure gas filled in the second housing lower cylinder 122 enters the suction chamber through the first suction chamber communicating passage 161 which starts to open at the moment when the piston 14 passes the positon shown in FIG. 2B, and the pressure of the back pressure chamber decreases.

(58) If the pressure of the back pressure chamber decreases, then F1 increases in the equation (1), and F2 decreases in the equation (4). Such back pressure decrease continues until the first suction chamber communicating passage 161 is in an open state. And then, F2 is nearly equal to F1 or a moment when the force is reversed as F1>F2 minutely arrives, and at this time, the piston 14 moves downward continuously till the first suction chamber communicating passage 161 is closed. In this time, the reaction force of the first elastic unit 21 helps the piston 14 to move downward.

(59) Finally, the piston 14 reaches a new equilibrium state, and the back pressure Pb becomes a new set back pressure value satisfying the equation (9) in a new running condition. The piston 14 is placed at the positon between positions shown in FIGS. 2B and 2C, that is, the position shown in FIG. 2E.

(60) As shown above, the back pressure regulating valve according to the present invention may make the back pressure have always a value given by the equation (9) regardless of various changes of the running condition such as an increase or a decrease of the discharging pressure, or an increase or decrease of the suction pressure. If the discharging pressure Pd and the suction pressure Ps are given in the equation (9), the back pressure Pb is determined according to the pressure ratio rp. However, the pressure ratio rp defined in the equation (8) has a fixed value determined by the cross sectional sizes A1, A2 of the first piston 141 and second piston 142 corresponding to the shape dimension of the piston and the cross sectional size A0 of the connecting rod 143.

(61) For example, if the diameter of the first piston 141 is 5 mm, the diameter of the second diameter is 7.35 mm, and the diameter of the connecting rod 143 is 2 mm, then the pressure ration (rp) becomes 2.0 and is expressed as the equation (10) below.

(62) $\begin{array}{cc}\frac{P_d-P_b}{P_b-P_s}=2.0& \left(10\right)\end{array}$

(63) If rp=2.0, then the back pressure is expressed as the equation (11) below.

(64) $\begin{array}{cc}{P}_b=\left(P_d+2P_s\right)/3& \left(11\right)\end{array}$

(65) The first piston 141, the second piston 142 and the connecting rod 143 may have various values, but not limited to.

(66) While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the appended claims.