spiral compressor

Abstract

Spiral compressor (1), comprising: a stationary spiral (15) comprising a spiral wall section arranged upright on a side face of an end plate (15A); a circumferential spiral (16) comprising a spiral wall section which is arranged upright on a side surface of an end plate (16A), wherein the circumferential spiral (16) is supported in such a way that it can perform a circumferential movement with the two wall sections engaging with each other, while preventing self-rotation; an outlet opening (18) through which a fluid compressed by the two spirals (15,16) is discharged; an end-plate step section (16E) formed at the end plate (16A) by one of the two spirals (15, 16), such that on one side surface a height along the spiral (16) of the wall section is higher on a middle section side and lower on an outer end side; and a wall section step section (15E) formed on the wall section by the other of the two spirals (15,16) corresponding to the end plate step section (16E), such that a height along the spiral (15) of the wall section is lower on a middle section side and higher on an outer end side; characterized by the fact that the spiral (16) on which the end plate step section (16E) is provided has been subjected to surface hardening, and the other spiral (15) has not been subjected to surface hardening, wherein Ls / Lout is 0.05 or greater, where Lout is a height of the wall section formed with a greater height on the outer end side, and Ls is a height of the end plate step section (16E) formed with a greater height on the middle section side.

Description

[0001] The present invention relates to a three-dimensional spiral compressor.

[0002] Generally, scroll compressors are designed with a pair of stationary and rotating scrolls. Each scroll includes an end plate with a spiral turn mounted upright on it. The stationary and rotating scrolls are engaged, with their spiral turns (spiral wall section) facing each other at a 180° phase difference. In this configuration, the scroll compressor can form a sealed compression chamber between the scrolls and compress the fluid. In such spiral compressors, a two-dimensional compression structure is usually used in which the pitch of the spiral turns of the stationary spiral and the rotating spiral is constant over the entire length in the spiral direction, and it is caused that a compression chamber moves from the outer circumferential side to the inner circumferential side while its capacity is gradually reduced, and the fluid is compressed in the circumferential direction of the spiral turns.

[0003] To improve the efficiency of the spiral compressor and achieve a reduction in size and weight, a three-dimensional spiral compressor is provided. This three-dimensional spiral compressor has a structure in which a stage section is provided at a predetermined position along the spiral direction on the tip and base surfaces of the spiral turns of both the stationary and rotating spirals. This stage section forms a boundary where the height of the spiral turns transitions from higher on the outer circumferential side to lower on the inner circumferential side, and the height of the compression chamber also transitions from higher on the outer circumferential side of the spiral turns to lower on the inner circumferential side in the axial direction. This structure enables the fluid to be compressed both circumferentially and vertically along the spiral turns.

[0004] These three-dimensional spiral compressors are known, an example of which is described in JP 2002-5052A. In this three-dimensional spiral compressor, an end-plate stage section is formed in a stationary spiral and a rotating spiral, and a winding stage section corresponding to the end-plate stage section is formed in the spiral winding of the stationary spiral and the rotating spiral.

[0005] Another example is given in JP S60 - 17956 B (see Fig. 8) described. In this three-dimensional spiral compressor, an end-plate stage section is provided in a stationary spiral or a rotating spiral, and a winding stage section corresponding to the end-plate stage section is formed in the spiral winding of the other spiral.

[0006] To prevent wear and seizing due to contact between the spiral turns of the spirals, one or both spirals are usually subjected to surface hardening using a coating or the like. JP 2007 - 255 191 A (see

[0046] ) describes such an example in which a coating is applied to the stage sections of the three-dimensional spiral compressor.

[0007] A spiral compressor with the features of the preamble of claim 1 is known from US patent 2006 / 0 140 804 A1.

[0008] From JP 2008 - 151 009 A a spiral compressor is known in which a wall section and / or a bottom section of a rotating spiral and / or a stationary spiral is / are provided with a hardening surface coating.

[0009] From JP 2014 - 009 593 A a spiral compressor is known in which an end plate stage section and a wall section stage section of approximately the same height are provided on a stationary spiral or a rotating spiral.

[0010] As in the technology of JP 2002-5052A, a configuration in which step sections provided on a fixed spiral and a rotating spiral have the same height results in both spirals having the same shape. Therefore, the effect of a surface hardening treatment does not change depending on whether the fixed spiral or the rotating spiral is treated.

[0011] After thorough research, the inventors discovered that if the height of the step sections of the stationary and rotating spirals differs, the shape of the spirals also differs. Furthermore, depending on whether one of the spirals has undergone surface hardening, or whether one spiral has been surface hardened to achieve a harder surface than the other, different results can be expected. In other words, they discovered that a corresponding surface hardening treatment is required depending on the height difference of the step sections, taking into account the contact between the end plate step section and the winding step section.

[0012] In a similar manner to the technology of JP S60 - 17956 B, the same problems described above apply in a configuration in which an end plate step section is provided in a stationary spiral or a rotating spiral, and a turn step section corresponding to the end plate step section is formed in the spiral turn of the other spiral.

[0013] In view of the foregoing circumstances, an objective of the present invention is to reduce the wear of a spiral compressor by means of a spiral that has been subjected to a corresponding surface hardening treatment.

[0014] A spiral compressor according to the present invention has the features of claim 1, claim 2, claim 3 or claim 4 to solve the problems described above.

[0015] In the spiral compressor according to claim 1, in which the end-plate stage section is provided on the stationary spiral or the rotating spiral, and the wall-section stage section is provided on the other spiral, the shapes of the stationary spiral and the rotating spiral are asymmetrical and do not have the same shape. During the rotating motion in engagement between the stationary spiral and the rotating spiral, the wall-section stage section and the end-plate stage section are in contact and move relative to each other. The end-plate stage section has a larger contact surface. If the end-plate stage section is treated with a surface hardening treatment, the wear of the surface hardening treatment can be significantly reduced, thereby preventing seizing.

[0016] Furthermore, the wall section, which incorporates the wall section-step section, exhibits a stress concentration at the root of the wall section-step section. However, the surface hardening treatment increases the surface roughness, and consequently, the stress concentration at the root of the wall section-step section can be reduced. Therefore, the spiral incorporating the wall section-step section is not subjected to surface hardening.

[0017] For surface hardening, a hard alumite treatment can be used, for example, in embodiments where the stationary spiral and the rotating spiral are made of an aluminum alloy. Furthermore, in embodiments where the stationary spiral and the rotating spiral are made of cast iron or iron, a phosphate coating or a diamond-like coating (DLC) can be used.

[0018] In embodiments where the end plate step section is provided on the circumferential spiral and the wall section step section is provided on the stationary spiral, the circumferential spiral is subjected to surface hardening, for example, and the stationary spiral is not subjected to surface hardening.

[0019] In the spiral compressor according to claim 2, in which the end plate step section is formed on the stationary spiral and the rotating spiral, the wall section step sections corresponding to the end plate step sections are formed on the wall sections of the stationary spiral and the rotating spiral, and the corresponding end plate step sections and the wall section step sections each have different heights, the shapes of the stationary spiral and the rotating spiral are asymmetrical and they do not have the same shape.

[0020] During the rotational movement, the stationary spiral and the rotating spiral engage with each other, and the wall section step and the end plate step are in contact and move relative to each other. The end plate step has a larger contact surface. If the spiral with the taller end plate step is treated with a surface hardener, the wear of the surface treatment can be significantly reduced, thus preventing seizing.

[0021] Furthermore, the wall section, which incorporates the wall section step, exhibits a stress concentration at the root of the wall section step. However, the surface hardening treatment increases the surface roughness, and consequently, the stress concentration at the root of the wall section step can be reduced. Therefore, the spiral with the higher wall section step is not subjected to surface hardening.

[0022] For surface hardening treatment, in embodiments where the stationary spiral and the rotating spiral are made of an aluminum alloy, a hard aluminite treatment can be used, for example.

[0023] In embodiments where the end plate step section provided on the circumferential spiral is higher than the end plate step section provided on the stationary spiral, the circumferential spiral, for example, has been subjected to surface hardening and the stationary spiral has not been subjected to surface hardening.

[0024] In the spiral compressor according to claim 3, in which the end plate stage section is provided on the stationary spiral or the rotating spiral, and the wall section stage section is provided on the other spiral, the shapes of the stationary spiral and the rotating spiral are asymmetrical and do not have the same shape.

[0025] During the rotational movement, the stationary spiral and the rotating spiral engage with each other, and the wall section step and the end plate step are in contact and move relative to each other. The end plate step has a larger contact surface. If the spiral with the end plate step is treated with a surface hardener to create a harder surface than the other spiral, the wear of the surface hardening treatment can be significantly reduced, thus preventing seizing.

[0026] In embodiments where the stationary spiral and the rotating spiral are made of an aluminum alloy, for example a Ni-P (nickel-phosphorus) coating can be used for the surface hardening treatment for a harder surface, and a Sn (tin) coating can be used for the other surface.

[0027] In embodiments where the end plate step section is provided on the circumferential spiral and the wall section step section is provided on the stationary spiral, the circumferential spiral is subjected to surface hardening so that it has a harder surface than the stationary spiral.

[0028] In the spiral compressor according to claim 4, in which the end plate step section is formed on the stationary spiral and the rotating spiral, the wall section step sections corresponding to the end plate step sections are formed on the wall sections of the stationary spiral and the rotating spiral, and the corresponding end plate step sections and the wall section step sections each have different heights, the shapes of the stationary spiral and the rotating spiral are asymmetrical and they do not have the same shape.

[0029] During the rotational movement, the stationary and rotating spirals engage with each other, and the wall section step and the end plate step are in contact and move relative to each other. The end plate step has a larger contact surface. If the spiral with the taller end plate step is treated with a surface hardener to create a harder surface than the other spiral, the wear on the surface treatment can be significantly reduced, thus preventing seizing.

[0030] In embodiments where the stationary spiral and the rotating spiral are made of an aluminum alloy, for example a Ni-P (nickel-phosphorus) coating can be used for the surface hardening treatment for a harder surface, and a Sn (tin) coating can be used for the other surface.

[0031] In embodiments where the end plate step section provided on the circumferential spiral is higher than the end plate step section provided on the stationary spiral, the circumferential spiral is subjected to surface hardening so that it has a harder surface than the stationary spiral.

[0032] A spiral compressor according to the present invention is configured such that Ls / Lout is 0.05 or greater, where Lout is the height of the wall section formed with a greater height on the outer end side, and Ls is the height of the end plate stage section formed with a greater height on the middle section side.

[0033] An advantageous modification of the present invention is found in dependent claim 5.

[0034] The current inventors considered Ls / Lout, a value of the height Ls of the end-plate step section on the middle section side divided by the height Lout of the wall section on the outer end side. They discovered that when Ls / Lout is large, the dimensions of the step increase. This could lead to a performance drop caused by an increase in the path through which the compaction fluid can escape.

[0035] If Ls / Lout is small, the dimensions of the step are reduced. This can lead to a decrease in the compaction ratio and a relatively high reduction in the thickness of the wall section due to the height of the wall section on the middle section side. You have found that Ls / Lout is preferably 0.05 or greater. Ls / Lout should ideally be in the range between 0.05 and 0.3, and preferably in the range between 0.1 and 0.2.

[0036] Note that the height Lout of the wall section designed to be higher on the outer end specifically refers to the height of the wall section with a step in its highest position (in other words, on the outer end). The height Ls of the end-plate step section on the middle section side specifically refers to the height of the end plate with a step in its highest position, measured from the lowest position of the end plate (in other words, on the outer end).

[0037] If the spiral provided with the end plate step section, or the spiral with the higher end plate step section, is subjected to surface hardening, the wear of the surface hardening treatment can be reduced and seizing can be prevented.

[0038] If the spiral provided with the end plate step section, or the spiral with the higher end plate step section, is subjected to surface hardening so that it has a harder surface than the other spiral, the wear of the surface hardening treatment can be reduced and seizing can be prevented. Fig. Figure 1 is a vertical cross-sectional view of a spiral compressor according to an embodiment of the present invention. Fig. Figure 2 is a horizontal cross-sectional view of the way in which a stationary spiral and a rotating spiral engage with each other. Fig. Figure 3 is an enlarged horizontal cross-sectional view of an end plate step section and a coil step section. Fig. Figure 4 is an enlarged vertical cross-sectional view of the end plate step section and the coil step section. Fig. Figure 5 is an enlarged perspective view of the coil step section.

[0039] The embodiments of the present invention are described below with reference to the drawings. As shown in Fig. As shown in Figure 1, a scroll compressor 1 comprises a housing 2 that defines the outside of the scroll compressor 1. The housing 2 is a cylinder with an open front end (left side in the drawing) and a sealed rear end. By tightening and securing a front housing 3 in the opening on the front end using screws 4, a sealed space is formed inside the housing 2, and a scroll compression mechanism 5 and a drive shaft 6 are installed in the sealed space.

[0040] The drive shaft 6 is rotatably supported by the front housing 3 via a main bearing 7 and an auxiliary bearing 8. A pulley 11, rotatably mounted on an outer circumferential section of the front housing 3 via a bearing 10, is connected via an electromagnetic coupling 12 to a front end section of the drive shaft 6, which projects from the outside of the front housing 3 via a mechanical seal 9, such that the drive force can be transmitted from an external source.

[0041] A crankpin 13, which is eccentric by a predetermined dimension, is integrally provided at the rear end of the drive shaft 6 and is connected to a circumferential spiral 16 of the spiral compression mechanism 5 described below via a known subordinate crank mechanism 14, which includes a drive sleeve and a drive bearing that allow a variable radius of rotation.

[0042] In the spiral compression mechanism 5, a pair of compression chambers 17 is formed between a stationary spiral 15 and the rotating spiral 16. The pair of compression chambers 17 are located opposite each other on either side of the center of the stationary spiral 15, as the stationary and rotating spirals 15 and 16 are engaged with each other at a 180° phase difference. The spiral compression mechanism 5 is configured to compress a fluid (refrigerant gas) by moving each of the compression chambers 17 from an outer circumferential position towards a central position, while its capacity is gradually reduced.

[0043] An outlet opening 18, which releases compressed gas, is provided in a central section of the stationary spiral 15, and the stationary spiral 15 is fixedly attached to a bottom wall surface of the housing 2 by means of screws 19. Furthermore, the rotating spiral 16 is connected to the crankpin 13 of the drive shaft 6 via the subordinate crank mechanism 14 and is supported by a thrust bearing surface of the front housing 3 via a known self-rotating prevention mechanism 20, such that the rotating spiral 16 can rotate freely.

[0044] An O-ring 21 is provided around the outer circumference of an end plate 15A of the stationary spiral 15. Because the O-ring 21 comes into close contact with the inner circumferential surface of the housing 2, the interior of the housing 2 is divided into an outlet chamber 22 and an inlet chamber 23.

[0045] The outlet opening 18 opens into the outlet chamber 22. The compressed gas from the compression chambers 17 is released through the outlet opening 18 and then discharged to one side of the cooling circuit.

[0046] An inlet opening 24, provided in the housing 2, opens into the inlet chamber 23. A low-pressure gas that has flowed through the cooling circuit is drawn through the inlet opening 24 into the inlet chamber 23, and then the refrigerant gas is drawn into the interior of the compression chambers 17 via the inlet chamber 23.

[0047] The pair of stationary spiral 15 and rotating spiral 16 comprises spiral turns 15B and 16B, each of which is integrally formed as wall sections in an upright position on the end plate 15A and an end plate 16A, respectively. A wingtip surface 15C of the stationary spiral 15 is in contact with a wing base surface 16D of the rotating spiral 16, and a wingtip surface 16C of the rotating spiral 16 is in contact with a wing base surface 15D of the stationary spiral 15.

[0048] An end-plate step section 16E is provided on the end plate 16A of the circumferential spiral 16 such that the height of the end plate 16A transitions from higher on the middle section side to lower on the outer end side in the spiral direction of the spiral turn 16B. In particular, as shown in Fig. As shown in Figure 2, the end plate step section 16E is provided at a position that is 180° from the position where the spiral turn 16B of the circumferential spiral 16 ends.

[0049] A winding step section 15E is provided on the spiral turn 15B of the stationary spiral 15 such that it corresponds to the end-plate step section 16E of the circumferential spiral 16 described above, such that the height of the spiral turn 15B transitions from lower on the middle section side of the spiral to higher on the outer end side. In particular, as shown in Fig. As shown in Figure 2, the winding step section 15E is provided in a position that is 360° from the position where the spiral winding 15B of the stationary spiral 15 ends.

[0050] In other words, the end plate step section 16E is provided only on the end plate 16A of the rotating spiral 16, and the winding step section 15E is provided only on the spiral winding 15B of the stationary spiral 15.

[0051] Therefore, no stepped section is provided on the spiral turn 16B of the rotating spiral 16, and the tip end of the spiral turn 16B has a uniform height. Furthermore, no stepped section is provided on the end plate 15A of the stationary spiral 15, resulting in a flat surface for the end plate 15A.

[0052] As in Fig. As shown in Figure 2, the compression chambers 17 are formed from at least one pair of compression chambers 17A, 17B, which are opposite each other on each side of the center of the stationary spiral 15.

[0053] The stationary spiral 15 and the circumferential spiral 16 described above are made of an aluminum alloy. The stationary spiral 15 is not subjected to any surface hardening, and after cutting and finishing, the aluminum alloy forms the outermost surface layer. The circumferential spiral 16 is subjected to surface hardening using a hard aluminum treatment.

[0054] As in Fig. 3 and Fig. As shown in Figure 4, a hard aluminite layer C is formed on the end plate step section 16E of the circumferential spiral 16, and the winding step section 15E of the stationary spiral 15 was not subjected to any surface hardening.

[0055] When the rotating spiral 16 revolves relative to the stationary spiral 15, as in Fig. As shown in Figure 3, the end plate step section 16E and the winding step section 15E move relative to each other while in contact. Consequently, the curved surface of the tip end of the winding step section 15E comes into contact with the curved surface of the end plate step section 16E, which has a larger radius.

[0056] For surface hardening, at least a region of the circumferential spiral 16, which comes into contact with the stationary spiral 15, is treated, and preferably a region is treated that comprises the entirety of the spiral turn 16B and the entirety of the end plate 16A on the side where the spiral turn 16B is provided. The entire circumferential spiral 16 can, of course, be subjected to surface hardening.

[0057] Note that reference 31 in Fig. 4 to indicate a tip seal to prevent fluid leakage, which is formed in the groove at the tip end of the spiral winding 15B.

[0058] Ls / Lout is 0.05 or greater, where the height of the spiral turn 15B, which is formed to be higher on the outer end of the fixed spiral 15, in other words, the height on the outside of the turn step section 15E, is Lout (see Fig. 1), and the height of the end plate step section 16E, which is formed to be higher on the middle section side of the circumferential spiral 16, in other words, the height of the step on the middle section side of the end plate step section 16E, Ls is (see Fig. 1) Furthermore, Ls / Lout is preferably in a range between 0.05 and 0.3, and at best in a range between 0.1 and 0.2.

[0059] According to the spiral compressor 1 of the present embodiment, the following effects are achieved.

[0060] During the rotating motion, the stationary spiral 15 and the rotating spiral 16 engage with each other, and the winding step section 15E and the end plate step section 16E are in contact and move relative to each other. The end plate step section 16E has a larger contact surface than the winding step section 15E, which has a curved surface with a smaller radius than the end plate step section 16E. If the end plate step section 16E is subjected to a hard alumite treatment, the wear of the hard alumite layer C can be significantly prevented, thus preventing seizing.

[0061] Furthermore, the spiral turn 15B, which is provided with the turn step section 15E, is subject to a load concentration at a root 15F of the turn step section 15E. However, the hard Alumit treatment increases the surface roughness, and consequently, the load intensity at the root 15F of the turn step section 15E can be reduced. Therefore, the load intensity can be improved by not subjecting the stationary spiral, including the turn step section 15E, to surface hardening.

[0062] The Ls / Lout ratio of the height Ls of the end-plate stage section 16E on the middle section side divided by the height Lout of the spiral coil 15B on the outer end side is 0.05 or greater, and preferably in a range between 0.05 and 0.3, and most ideally in a range between 0.1 and 0.2. If Ls / Lout is large, the stage dimensions increase, and a performance drop can occur due to an increase in the path through which the compaction fluid can exit. However, with the dimensions described above, this performance drop can be substantially prevented. If Ls / Lout is small and the stage dimensions are reduced, the compaction ratio decreases, and a drop in spiral coil thickness can occur because the spiral coil height on the middle section side is relatively high. With the dimensions described above, this reduction in thickness can be substantially prevented.

[0063] Note that in the embodiment described above, the end plate step section 16E is provided only at the end plate 16A of the rotating spiral 16, and the winding step section 15E is provided only at the spiral turn 15B of the stationary spiral 15. However, in other embodiments of the present invention, the opposite may be true, in which an end plate step section is provided only at the end plate 15A of the stationary spiral 15, and a winding step section is provided only at the spiral turn 16B of the rotating spiral 16. In this embodiment, the stationary spiral 15 has been surface hardened, and the rotating spiral 16 has not.

[0064] Furthermore, in the embodiment described above, the spirals 15, 16 are made of an aluminum alloy. However, in embodiments where the spirals 15, 16 are made of cast iron or iron, a phosphate coating or a diamond-like coating (DLC) and thus a surface hardening treatment can be used.

[0065] In the embodiment described above, only one spiral was subjected to surface hardening. However, in other embodiments, both spirals can be surface hardened. In such embodiments, the spiral with an end plate step section is surface hardened to give it a harder surface than the other spiral. For example, a Ni-P (nickel-phosphorus) coating can be used for the surface hardening treatment of one harder surface, and a Sn (tin) coating can be used for the other.

[0066] Furthermore, in another embodiment, a spiral compressor such as that described in JP 2002-5052 A, which is provided with an end-plate step section at the end plates of the stationary spiral and the rotating spiral, can be used. In other words, if the height of the end-plate step section provided at the end plate of the rotating spiral is greater than that of the end-plate step section provided at the end plate of the stationary spiral, the rotating spiral has, for example, been surface-hardened and the stationary spiral has not. Alternatively, the rotating spiral is surface-hardened so that it has a harder surface than the stationary spiral.

[0067] If the height of the end-plate step section provided on the end plate of the stationary spiral is greater than that of the end-plate step section provided on the end plate of the rotating spiral, then, for example, the stationary spiral has undergone surface hardening and the rotating spiral has not. Alternatively, the stationary spiral is surface hardened to give it a harder surface than the rotating spiral. List of reference symbols 1 spiral compressor 15 Fixed spirals 16 Circulating spirals 15A, 16A end plate 15B, 16B spiral winding 15C, 16C wingtip area 15D, 16D wing base area 15E Winding section (wall section-step section) 16E End plate step section 17 Compression chamber 17A Front compression chamber 17B Rear compression chamber

Claims

[1] Spiral compressor (1), comprising: a stationary spiral (15) comprising a spiral wall section arranged upright on a side face of an end plate (15A); a circumferential spiral (16) comprising a spiral wall section arranged upright on a side surface of an end plate (16A), wherein the circumferential spiral (16) is supported in such a way that it can perform a circumferential movement with the two wall sections engaging with each other, while preventing self-rotation; an outlet opening (18) through which a fluid compressed by the two spirals (15,16) is discharged; an end-plate step section (16E) formed at the end plate (16A) by one of the two spirals (15, 16), such that on one side surface a height along the spiral (16) of the wall section is higher on a middle section side and lower on an outer end side; and a wall section step section (15E) formed on the wall section by the other of the two spirals (15,16) corresponding to the end plate step section (16E), such that a height along the spiral (15) of the wall section is lower on a middle section side and higher on an outer end side; characterized by , that the spiral (16) on which the end plate step section (16E) is provided has been subjected to surface hardening, and the other spiral (15) has not been subjected to surface hardening, wherein Ls / Lout is 0.05 or greater, where Lout is a height of the wall section formed with a greater height on the outer end side, and Ls is a height of the end plate step section (16E) formed with a greater height on the middle section side. [2] Spiral compressor (1), comprising: a stationary spiral (15) comprising a spiral wall section arranged upright on a side face of an end plate (15A); a circumferential spiral (16) comprising a spiral wall section which is arranged upright on a side surface of an end plate (16A), wherein the circumferential spiral (16) is supported in such a way that it can perform a circumferential movement with the two wall sections engaging with each other, while preventing self-rotation; an outlet opening (18) through which a fluid compressed by the two spirals (15,16) is discharged; an end-plate step section (16E) formed at the respective end plate (15A, 16A) of the two spirals (15, 16) such that on one side surface the height along the spiral (15, 16) of the wall sections is higher on a middle section side and lower on an outer end side; and a wall section step section (15E) which is formed on the respective wall section of the two spirals (15,16) corresponding to the end plate step sections (16E), such that a height along the spiral (15,16) is lower on a middle section side and higher on an outer end side; wherein the end plate step section (16E) of one of the spirals (15,16) and the end plate step section (16E) of the other of the spirals (15,16) have different heights; characterized by , that the spiral (15,16) which has the higher end plate step section (16E) of the corresponding end plate step sections (16E) has been subjected to surface hardening and the other spiral (15,16) has not been subjected to surface hardening, wherein Ls / Lout is 0.05 or greater, where Lout is a height of the wall section formed with a greater height on the outer end side, and Ls is a height of the end plate step section (16E) formed with a greater height on the middle section side. [3] Spiral compressor (1), comprising: a stationary spiral (15) comprising a spiral wall section arranged upright on a side face of an end plate (15A); a circumferential spiral (16) comprising a spiral wall section which is arranged upright on a side surface of an end plate (16A), wherein the circumferential spiral (16) is supported in such a way that it can perform a circumferential movement with the two wall sections engaging with each other, while preventing self-rotation; an outlet opening (18) through which a fluid compressed by the two spirals (15,16) is discharged; an end-plate step section (16E) formed at the end plate (15A, 16A) by one of the two spirals (15, 16), such that on one side face, a height along the spiral (15, 16) of the wall section is higher on a middle section side and lower on an outer end side; and a wall section step section (15E) formed on the wall section by the other of the two spirals (15,16) corresponding to the end plate step section (16E), such that a height along the spiral (15,16) of the wall section is lower on a middle section side and higher on an outer end side; characterized by , that Both spirals (15, 16) were subjected to surface hardening, wherein the spiral (16) on which the end plate step section (16E) is provided was treated such that it has a harder surface than that of the other spiral (15), wherein Ls / Lout is 0.05 or greater, where Lout is a height of the wall section formed with a greater height on the outer end side, and Ls is a height of the end plate step section (16E) formed with a greater height on the middle section side. [4] Spiral compressor (1), comprising: a stationary spiral (15) comprising a spiral wall section arranged upright on a side face of an end plate (15A); a circumferential spiral (16) comprising a spiral wall section arranged upright on a side surface of an end plate (16A), wherein the circumferential spiral (16) is supported in such a way that it can perform a circumferential movement with the two wall sections engaging with each other, while preventing self-rotation; an outlet opening (18) through which a fluid compressed by the two spirals (15,16) is discharged; an end plate step section (16E) formed at the respective end plate (15A, 16A) by one of the two spirals (15, 16), such that on one side surface the height along the spiral (15, 16) of the wall sections is higher on a middle section side and lower on an outer end side; and a wall section step section (15E) which is formed on the respective wall section of the two spirals (15,16) corresponding to the end plate step sections (16E), such that a height along the spiral (15,16) of the wall section is lower on a middle section side and higher on an outer end side; wherein the end plate step section (16E) of one of the spirals (15,16) and the end plate step section (16E) of the other of the spirals (15,16) have different heights; characterized by , that Both spirals (15, 16) were subjected to surface hardening, wherein the spiral (15, 16) which has the higher end plate step section (16E) of the corresponding end plate step sections (16E) was subjected to surface hardening such that it has a harder surface than that of the other spiral (15, 16), wherein Ls / Lout is 0.05 or greater, where Lout is a height of the wall section formed with a greater height on the outer end side, and Ls is a height of the end plate step section (16E) formed with a greater height on the middle section side. [5] Spiral compressor (1) according to any one of claims 1 to 4, wherein Ls / Lout is 0.1 or greater, where Lout is a height of the wall section formed with a greater height on the outer end side, and Ls is a height of the end plate step section (16E) formed with a greater height on the middle section side.

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