Screw compressor

Abstract

The invention provides a screw compressor capable of increasing the suction amount under the condition that the torsion angle of a rotor is small. A screw compressor is provided with a plurality of male rotor-side working chambers (10A) formed in a plurality of tooth spaces of a male rotor (1A), and a plurality of female rotor-side working chambers (10B) formed in a plurality of tooth spaces of a female rotor (1B). The rotation angle range of the female rotor (1B) in which the female rotor-side working chamber having the maximum volume among the plurality of female rotor-side working chambers (10B) is located is larger than the product of the number obtained by subtracting the number of teeth of the male rotor (1A) from the number of teeth of the female rotor (1B) and the rotation angle range of the female rotor (1B) corresponding to the circumferential width of the tooth space of the female rotor (1B). The suction completion time of the female rotor-side working chamber 10B is set later than a reference time at which the volume of the female rotor-side working chamber 10B becomes maximum, and is set before the propagation time of the pressure waves in the female rotor-side working chamber 10B from the discharge-side end surface 18B of the teeth 3B of the female rotor 1B to the suction-side end surface 19B elapses.

Description

Technical Field

[0001] This invention relates to a screw compressor. Background Technology

[0002] The screw compressor of Patent Document 1 includes: a male rotor having teeth with multiple grooves; a female rotor having teeth with multiple grooves and configured to mesh with the male rotor; multiple male rotor-side chambers formed in the multiple grooves of the male rotor; and multiple female rotor-side chambers formed in the multiple grooves of the female rotor.

[0003] The male rotor-side chamber and the female rotor-side chamber move and change volume as the male and female rotors rotate. The male rotor-side chamber and the female rotor-side chamber sequentially perform the intake stroke (drawing gas from the intake flow path through the intake port (opening), the compression stroke (compressing the gas by reducing its volume), and the discharge stroke (discharging the compressed gas into the discharge flow path through the discharge port (opening).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 06-288369 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] In Patent Document 1, the completion time of the intake of the female rotor-side chamber is the same as or earlier than the reference time when the volume of the female rotor-side chamber becomes the largest. However, if it is delayed, the intake volume may increase due to the inertia of the intake gas. However, if the condition of the following equation (1) is not met, the completion time of the intake of the female rotor-side chamber cannot be later than the reference time.

[0009] δf>(Zf-Zm)×(360 / Zf)…(1)

[0010] In equation (1), δf [degrees] represents the rotation angle range of the female rotor containing the female rotor chamber with the largest volume among multiple female rotor side chambers (hereinafter referred to as the female rotor side maximum volume existence angle). The boundary line between the wall of the male rotor side cavity and the wall of the female rotor side cavity is called the low-pressure side cusp and the high-pressure side cusp. The rotation angle range φCf [degrees] of the female rotor corresponding to the circumferential width between the low-pressure side cusp and the high-pressure side cusp is defined. The male rotor teeth exist within this female rotor rotation angle range φCf, therefore the volume of the female rotor side chamber cannot be the maximum. Therefore, the female rotor side maximum volume existence angle δf is obtained by subtracting the female rotor torsion angle φAf [degrees] from the female rotor rotation angle range φBf [degrees] corresponding to the circumferential width of the female rotor side cavity wall (where φBf = 360 - φCf). The smaller the female rotor torsion angle φAf, the larger the female rotor side maximum volume existence angle δf.

[0011] The condition of equation (1) is that the maximum volume of the female rotor side exists at an angle δf, which is greater than the product of the number of teeth of the female rotor Zf minus the number of teeth of the male rotor Zm (Zf-Zm) and the rotation angle range of the female rotor corresponding to the circumferential width of the tooth groove of the female rotor (360 / Zf). If the torsion angle φAf of the female rotor is large and does not satisfy the condition of equation (1), then when the volume of the female rotor side chamber becomes the maximum, the male rotor side chamber connected to the female rotor side chamber is in the compression stroke. Therefore, it is possible to discharge the compressed air of the male rotor side chamber through the female rotor side chamber. Therefore, the intake completion time of the female rotor side chamber should not be later than the reference time.

[0012] On the other hand, if the twist angle φAf of the female rotor is small and satisfies the condition of equation (1), the intake completion time of the female rotor side chamber can be delayed compared to the reference time, thereby increasing the intake volume. However, when the female rotor side chamber reaches the discharge side end face of the female rotor teeth, it is reflected by the inner wall of the housing opposite to the discharge side end face of the female rotor teeth, generating a pressure wave (backflow) towards the intake side end face of the female rotor teeth. Therefore, if the intake completion time of the female rotor side chamber is too late, the aforementioned pressure wave is discharged through the intake port, and the intake volume is reduced.

[0013] The present invention was made in view of the above circumstances, and one of its objectives is to increase the intake volume under the condition that the twist angle of the female rotor is small.

[0014] Technical solutions for solving the problem

[0015] To address the aforementioned issues, the structure described in the scope of the claims is applied. The present invention includes several solutions for solving the above-mentioned problems. One example is a screw compressor comprising: a male rotor having teeth with multiple grooves; a female rotor having teeth with multiple grooves configured to mesh with the male rotor; a plurality of male rotor-side chambers formed in the multiple grooves of the male rotor; and a plurality of female rotor-side chambers formed in the multiple grooves of the female rotor, wherein the rotation angle range of the female rotor containing the female rotor-side chamber with the largest volume is greater than the product of the number of teeth of the female rotor minus the number of teeth of the male rotor and the rotation angle range of the female rotor corresponding to the circumferential width of the tooth groove of the female rotor; the suction completion time of the female rotor-side chamber is set to be later than the reference time when the volume of the female rotor-side chamber becomes the largest, and is set to be before the propagation time of the pressure wave in the female rotor-side chamber from the discharge side end face of the teeth of the female rotor to the suction side end face has elapsed.

[0016] Invention Effects

[0017] According to the present invention, the intake volume can be increased under the condition of a small rotor torsion angle.

[0018] Furthermore, the topics, structures, and effects not mentioned above are further clarified through the following explanation. Attached Figure Description

[0019] Figure 1 This is a cross-sectional view showing the structure of a screw compressor according to one embodiment of the present invention.

[0020] Figure 2 Based on Figure 1 Cross-sectional view of arrow II-II.

[0021] Figure 3 Based on Figure 2 Cross-sectional view of arrow III-III.

[0022] Figure 4 Based on Figure 2 The cross-sectional view of arrow IV-IV.

[0023] Figure 5 This is an unfolded view of the teeth of the female rotor, showing a plurality of female rotor-side chambers together with a portion of the suction port in one embodiment of the present invention.

[0024] Figure 6 This is an unfolded view of the teeth of the male rotor, showing a portion of the multiple male rotor-side chambers and the suction port in one embodiment of the present invention. Detailed Implementation

[0025] One embodiment of the present invention will be described with reference to the accompanying drawings.

[0026] Figure 1 This is a cross-sectional view showing the structure of the screw compressor in this embodiment (based on...). Figure 2 (Cross-sectional view of view II) Figure 2 Based on Figure 1 A cross-sectional view of view II-II. Figure 3 Based on Figure 2 A cross-sectional view of view III-III. Figure 4 Based on Figure 2 A cross-sectional view of IV-IV. Furthermore, in Figure 4 For simplicity, the diagrams of the discharge port and discharge flow path have been omitted.

[0027] The screw compressor of this embodiment includes a male rotor 1A, a female rotor 1B configured to mesh with the male rotor 1A, and a housing 2 that houses the male rotor 1A and the female rotor 1B.

[0028] The male rotor 1A includes: a tooth portion 3A having a plurality of (six in this embodiment) helical teeth and a plurality of tooth grooves formed therebetween; and an axial side thereof ( Figure 1 and Figure 2 The suction side shaft 4A is connected to the left side of the toothed part 3A; and the other side of the axial direction of the toothed part 3A is connected to the suction side shaft 4A. Figure 1 and Figure 2 The discharge side shaft 5A is connected to the right side of the male rotor 1A. The intake side shaft 4A of the male rotor 1A is rotatably supported by the intake side bearing 6A, and the discharge side shaft 5A of the male rotor 1A is rotatably supported by the discharge side bearing 7A.

[0029] The female rotor 1B includes: a tooth portion 3B having a plurality of (eight in this embodiment) helical teeth and a plurality of tooth grooves formed therebetween; and an axial side thereof ( Figure 2 The suction side shaft 4B is connected to the left side of the toothed part 3B; and the other side of the axial direction of the toothed part 3B is connected to the suction side shaft 4B. Figure 2 The discharge side shaft 5B is connected to the right side of the female rotor 1B. The suction side shaft 4B of the female rotor 1B is rotatably supported by the suction side bearing 6B, and the discharge side shaft 5B of the female rotor 1B is rotatably supported by the discharge side bearing 7B.

[0030] The intake-side shaft 4A of the male rotor 1A penetrates the housing 2 and is connected to the rotating shaft (not shown) of the motor. Thus, the rotational force of the motor is transmitted to the male rotor 1A, causing it to rotate. The teeth 3B of the female rotor 1B engage with the teeth 3A of the male rotor 1A. Alternatively, the teeth 3B of the female rotor 1B may be configured to engage with the teeth 3A of the male rotor 1A in a non-contact manner, but a pair of timing gears (not shown) are provided on the discharge-side shaft 5A of both the male rotor 1A and the female rotor 1B, and these timing gears mesh with each other. Thus, the rotational force of the male rotor 1A is transmitted to the female rotor 1B, causing it to rotate.

[0031] The housing 2 is, for example, composed of a main housing 8 and an intake-side housing 9 connected to the main housing 8. The main housing 8 has: a male rotor-side cavity 11A, which receives the teeth 3A of the male rotor 1A and forms a plurality of male rotor-side working chambers 10A in its plurality of tooth grooves; and a female rotor-side cavity 11B, which receives the teeth 3B of the female rotor 1B and forms a plurality of female rotor-side working chambers 10B in its plurality of tooth grooves. The male rotor-side cavity 11A and the female rotor-side cavity 11B partially overlap each other, and their boundary lines have a low-pressure side cusp 12 and a high-pressure side cusp 13.

[0032] The male rotor-side chamber 10A and the female rotor-side chamber 10B move and change volume as the male rotor 1A and female rotor 1B rotate. The male rotor-side chamber 10A and the female rotor-side chamber 10B sequentially perform an intake stroke (intake of gas, such as air, through intake port 14 (opening) from intake flow path 15), a compression stroke (compression of gas by reducing volume), and a discharge stroke (discharge of compressed gas, such as compressed air, to discharge flow path 17 through discharge port 16 (opening).

[0033] In this embodiment, due to the shortening of leakage time caused by the shortening of compression time, the torsion angle φAf of the male rotor 1A and the torsion angle φAm of the female rotor 1B are made smaller, satisfying the condition of the above equation (1). For example, since the torsion angle φAm of the female rotor 1B is 150°, the rotation angle range of the female rotor 1B corresponding to the circumferential width of the wall of the female rotor side cavity 11B is φBf = 285°, so the maximum volume existence angle δf of the female rotor side is 135°. The product of the number of teeth Zf of the female rotor 1B minus the number of teeth Zm of the male rotor 1A (Zf-Zm) and the rotation angle range of the female rotor 1B corresponding to the circumferential width of the tooth groove of the female rotor 1B (360 / Zf) is 90°, thus satisfying the condition of equation (1). Therefore, the suction completion time of the male rotor side chamber 10A can be later than the reference time, and the suction completion time of the female rotor side chamber 10B can also be later than the reference time.

[0034] First, use Figure 5This describes the moment when the suction of the female rotor-side chamber 10B is completed (in other words, the moment when the suction port 14 of the female rotor-side chamber 10B is closed by the sealing portion 20 of the suction-side housing 9).

[0035] Figure 5 This is an unfolded view of the teeth 3B of the female rotor 1B, showing a portion of the plurality of female rotor-side chambers 10B and the suction port 14 in this embodiment. Figure 5 The longitudinal direction is the axial direction of the tooth portion 3B of the female rotor 1B. Figure 5 The transverse direction is the circumferential direction of the teeth 3B of the female rotor 1B, and its position is represented by the rotation angle of the female rotor 1B (more specifically, the rotation angle is defined as 0 when the position of the straight line connecting the rotation center of the male rotor 1A and the rotation center of the female rotor 1B is set). Figure 5 In the diagram, multiple diagonal lines represent the multiple tooth tips that divide the multiple female rotor side chambers 10B, and the parts marked with shaded lines in the multiple female rotor side chambers 10B indicate the suction completion state.

[0036] In this embodiment, the completion time of suction in the female rotor-side chamber 10B is set later than the reference time when the volume of the female rotor-side chamber 10B becomes the maximum (in other words, the reference time when the volume of the female rotor-side chamber 10B changes from a state where it is not the maximum to a state where it is the maximum), and is set before the propagation time of the pressure wave within the female rotor-side chamber 10B from the discharge-side end face 18B of the tooth 3B to the suction-side end face 19B. Details will be explained below.

[0037] When the leading tooth tip of the leading tooth tip and the following tooth tip of the dividing female rotor side chamber 10B reach the low-pressure side tip 12 at the discharge side end face 18B of the tooth portion 3B of the female rotor 1B, a pressure wave (countercurrent) is generated towards the suction side end face 19B of the tooth portion 3B of the female rotor 1B by being reflected by the inner wall of the main housing 8 opposite to the discharge side end face 18B of the tooth portion 3B of the female rotor 1B. The propagation time of the pressure wave from the discharge side end face 18B of the tooth portion 3B of the female rotor 1B to the suction side end face 19B is obtained by dividing the tooth groove length Lf of the female rotor 1B by the sound speed a. Therefore, with the position of the low-pressure side tip 12 as a reference, the rotation angle φLMTf of the female rotor 1B that the pressure wave advances from the discharge side end face 18B of the tooth portion 3B of the female rotor 1B to the suction side end face 19B (hereinafter referred to as the female rotor side countercurrent limit angle φLMTf) is obtained by the following equation (2). In the formula, ωf is the angular velocity of the male rotor 1B.

[0038] φLMTf=(Lf / a)×ωf …(2)

[0039] like Figure 5As shown, taking the position of the low-pressure side apex 12 as a reference, the position of the leading tooth tip in the discharge side end face 18B of the tooth 3B of the female rotor 1B is set, assuming the rotation angle φDf of the female rotor at the completion of suction in the female rotor side chamber 10B (hereinafter referred to as the female rotor side suction completion angle φDf). The female rotor side suction completion angle φDf is set to be less than the female rotor side countercurrent limit angle φLMTf. Therefore, the suction completion time of the female rotor side chamber 10B is set before the propagation time (Lf / a) of the pressure wave from the discharge side end face 18B of the tooth 3B of the female rotor 1B to the suction side end face 19B in the female rotor side chamber 10B has elapsed.

[0040] Next, use Figure 6 This describes the moment when the suction of the male rotor-side chamber 10A is completed (in other words, the moment when the suction port 14 of the male rotor-side chamber 10A is closed by the sealing portion 20 of the suction-side housing 9).

[0041] Figure 6 This is an unfolded view of the teeth 3A of the male rotor 1A, showing a portion of the plurality of male rotor-side chambers 10A and the intake port 14 in this embodiment. Additionally, Figure 6 The longitudinal direction is the axial direction of the tooth portion 3A of the male rotor 1A. Figure 6 The transverse direction is the circumferential direction of the teeth 3A of the male rotor 1A, and its position is represented by the rotation angle of the male rotor 1A (more specifically, the rotation angle is defined as 0° when the position of the straight line connecting the rotation center of the male rotor 1A and the rotation center of the female rotor 1B is set). Figure 6 In the diagram, multiple diagonal lines represent the multiple tooth tips that divide the multiple male rotor side chambers 10A, and the shaded parts in the multiple male rotor side chambers 10A indicate the suction completion state.

[0042] In this embodiment, the completion time of suction in the male rotor-side chamber 10A is set later than the reference time when the volume of the male rotor-side chamber 10A becomes the maximum (in other words, the reference time when the volume of the male rotor-side chamber 10A changes from a state where it is not the maximum to a state where it is the maximum), and is set before the propagation time of the pressure wave within the male rotor-side chamber 10A from the discharge-side end face 18A of the tooth portion 3A to the suction-side end face 19A. Details will be explained below.

[0043] When the leading tooth tip of the male rotor side chamber 10A reaches the low-pressure side tip 12 at the discharge side end face 18A of the tooth portion 3A of the male rotor 1A, it is reflected by the inner wall of the main housing 8 opposite to the discharge side end face 18A of the tooth portion 3A of the male rotor 1A, generating a pressure wave (countercurrent) towards the suction side end face 19A of the tooth portion 3A of the male rotor 1A. The propagation time of the pressure wave from the discharge side end face 18A of the tooth portion 3A of the male rotor 1A to the suction side end face 19A is obtained by dividing the tooth groove length Lm of the male rotor 1A by the sound speed a. Therefore, the rotation angle φLMTm of the male rotor 1A (hereinafter referred to as the male rotor side countercurrent limit angle φLMTm) that propagates from the position of the low-pressure side tip 12 until the pressure wave reaches the suction side end face 19A of the tooth portion 3A of the male rotor 1A is obtained by the following equation (3). In the formula, ωm is the angular velocity of the male rotor 1A.

[0044] φLMTm=(Lm / a)×ωm …(3)

[0045] like Figure 6 As shown, taking the position of the low-pressure side apex 12 as a reference, the position of the leading tooth tip in the discharge side end face 18A of the tooth 3A of the male rotor 1A is set, and the rotation angle φDm of the male rotor 1A at the completion of suction in the male rotor side working chamber 10A (hereinafter referred to as the male rotor side suction completion angle φDm) is assumed. The male rotor side suction completion angle φDm is set to be smaller than the male rotor side countercurrent limit angle φLMTm. Therefore, the suction completion time of the male rotor side working chamber 10A is set before the propagation time (Lm / a) of the pressure wave from the discharge side end face 18A of the tooth 3A of the male rotor 1A to the suction side end face 19B in the male rotor side working chamber 10A has elapsed.

[0046] As described above, in this embodiment, the intake completion time of the female rotor-side chamber 10B is set later than the reference time and before the pressure wave propagation time (Lf / a) has elapsed. Similarly, the intake completion time of the male rotor-side chamber 10A is set later than the reference time and before the pressure wave propagation time (Lm / a) has elapsed. Therefore, compared to the case where the intake completion times of the female rotor-side chamber 10B and the male rotor-side chamber 10A are not later than the reference time, the intake volume can be increased due to the inertia of the intake gas. Furthermore, unlike the case where the intake completion times of the female rotor-side chamber 10B and the male rotor-side chamber 10A are set after the pressure wave propagation time has elapsed, the pressure wave is not discharged through the intake port 14, thus preventing a decrease in the intake volume. Therefore, the intake volume can be increased even with a small rotor twist angle.

[0047] Furthermore, in one embodiment described above, an example was given where not only the intake completion time of the female rotor-side chamber 10B but also the intake completion time of the male rotor-side chamber 10A were later than the reference time, and were set before the pressure wave propagation time had elapsed. However, this is not the only limitation. Compared to the embodiment described above, although the overall intake volume is reduced, the intake completion time of the male rotor-side chamber 10A can also be set after the pressure wave propagation time has elapsed, or it can be the same as or earlier than the reference time.

[0048] Explanation of reference numerals in the attached figures

[0049] 1A…male rotor, 1B…female rotor, 3A, 3B…teeth, 10A…male rotor side chamber, 10B…female rotor side chamber, 11A…male rotor side cavity, 11B…female rotor side cavity, 18A, 18B…discharge side end face, 19A, 19B…suction side end face.

Claims

1. A screw compressor, characterized in that, include: A male rotor having teeth with multiple grooves formed; The female rotor has teeth with multiple grooves configured to mesh with the male rotor; Multiple male rotor side chambers formed in the multiple tooth grooves of the male rotor; and The plurality of female rotor side chambers formed in the plurality of tooth grooves of the female rotor, The rotation angle range of the female rotor containing the female rotor side chamber with the largest volume among the plurality of female rotor side chambers is greater than the product of the number of teeth of the female rotor minus the number of teeth of the male rotor and the rotation angle range of the female rotor corresponding to the circumferential width of the tooth groove of the female rotor. The completion time of suction in the female rotor-side chamber is set later than the reference time when the volume of the female rotor-side chamber reaches its maximum, and is set before the propagation time of the pressure wave from the discharge side end face of the teeth of the female rotor to the suction side end face in the female rotor-side chamber has elapsed.

2. The screw compressor according to claim 1, characterized in that: The intake completion time of the male rotor-side chamber is set later than the reference time when the volume of the male rotor-side chamber becomes the largest, and is set before the propagation time of the pressure wave from the discharge end face of the tooth of the male rotor to the intake end face in the male rotor-side chamber has elapsed.

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