Scroll compressor including end-plate side stepped portions of each of the scrolls corresponding to wall-portion side stepped portions of each of the scrolls

A scroll compressor with a stationary scroll, an orbiting scroll, and a discharge port through which a fluid that has been compressed by both the scrolls is discharged. An end plate of the orbiting scroll is provided with an end-plate side stepped portion formed such that, along a spiral of a spiral wrap, the height thereof increases toward a central side of the spiral and decreases toward an outer end side thereof. A spiral wrap of the stationary scroll is provided with a wall-portion side stepped portion formed corresponding to the end-plate side stepped portion such that the height thereof decreases toward the central side of the spiral and increases toward the outer end side thereof. A pair of compression chambers which face each other, the ventral side compression chamber communicates with the discharge port before the dorsal side compression chamber communicates with the discharge port.

TECHNICAL FIELD

The present invention relates to three-dimensional compression-type scroll compressors.

BACKGROUND ART

A scroll compressor is provided with a pair of a stationary scroll and an orbiting scroll. The scrolls each include an end plate with a spiral wrap disposed in an upright manner thereon. The spiral wraps (spiral wall portions) of the pair of the stationary scroll and the orbiting scroll are opposed and engaged with each other with a 180 degree phase difference, thus forming a sealed compression chamber between the scrolls. As a result, the scroll compressor is configured to compress fluid. The above-discussed scroll compressor generally has a two-dimensional compression structure in which the wrap heights of the spiral wraps of the stationary scroll and the orbiting scroll are set to be constant over the entire circumference in the spiral direction, a compression chamber is made to move from the outer circumferential side to the inner circumferential side while having its capacity gradually reduced, and the fluid having been sucked into the compression chamber is compressed in the circumferential direction of the spiral wraps.

Meanwhile, in order to improve efficiency of the scroll compressor and to achieve downsizing and weight-reduction thereof, a three-dimensional compression-type scroll compressor has been provided. Such a three-dimensional compression-type scroll compressor has a structure in which a stepped portion is provided at a predetermined position, along the spiral direction, on each of the tooth crest and the tooth base of the spiral wraps of the stationary scroll and the orbiting scroll, such that the stepped portion forms a boundary at which the wrap height of the spiral wraps shifts from higher on the outer circumferential side to lower on the inner circumferential side. By causing the height of the compression chamber in the axial direction to be higher on the outer circumferential side of the spiral wraps than on the inner circumferential side thereof, the fluid is compressed both in the circumferential direction and in the height direction of the spiral wraps.

As such a three-dimensional compression-type scroll compressor, for example, a scroll compressor in which an end-plate side stepped portion is formed on an end plate of each of a stationary scroll and an orbiting scroll, and a wrap side stepped portion corresponding to the end-plate side stepped portion is provided on a spiral wrap of each of the stationary scroll and the orbiting scroll is well-known, as described in Patent Literature 1.

Further, as described in Patent Literature 2, a scroll compressor in which an end-plate side stepped portion is provided on an end plate of one of a stationary scroll and an orbiting scroll, and a wrap side stepped portion corresponding to the end-plate side stepped portion is formed on a spiral wrap of the other of the scrolls is well-known.

CITATION LIST

Patent Literature

Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2002-5052A

SUMMARY OF INVENTION

Technical Problems

As described in Patent Literature 1, in the case where the stepped portions are provided in both the stationary scroll and the orbiting scroll and these stepped portions have the same height, the stationary and orbiting scrolls are formed in the same shape. As such, because capacities of a pair of compression chambers facing each other on either side of the center of the stationary scroll are theoretically equal to each other at every swivel angle, the pressures in these compression chambers become the same.

However, in the case where the heights of the stepped portions of the stationary scroll and the orbiting scroll are different from each other, both the scrolls are not formed in the same shape. Accordingly, because the capacities of the pair of compression chambers facing each other on either side of the center of the stationary scroll are not always equal to each other at every swivel angle, the pressures in the compression chambers differ from each other.

Likewise, as described in Patent Literature 2, also in the case where an end-plate side stepped portion is provided on an end plate of one of the stationary scroll and the orbiting scroll, and a wrap side stepped portion corresponding to the end-plate side stepped portion is provided on a spiral wrap of the other of the scrolls, the stationary and orbiting scrolls are not formed in the same shape. Accordingly, because the capacities of the pair of compression chambers facing each other on either side of the center of the stationary scroll are not always equal to each other at every swivel angle, the pressures in the compression chambers differ from each other.

As discussed above, in the case where the pressures in the pair of compression chambers facing each other on either side of the center of the stationary scroll are different, one of the compression chambers is excessively compressed in some case, which causes a reduction in compression efficiency.

In particular, in an intermediate period like the spring when a low pressure ratio is required, overcompression noticeably occurs in one of the compression chambers.

Having been conceived in light of such circumstances, an object of the present invention is to provide a scroll compressor capable of preventing overcompression.

Solution to Problem

A scroll compressor of the present invention employs the following methods to solve the problems described above.

The scroll compressor according to the present invention is provided with a stationary scroll including a spiral wall portion erected on one side surface of an end plate, an orbiting scroll that includes a spiral wall portion erected on one side surface of an end plate and is supported so as to be capable of orbital revolution movement while being prevented from self-rotation by the wall portions being engaged with each other, and a discharge port through which a fluid that has been compressed by both the scrolls is discharged. On the one side of the end plate of one of the scrolls, there is provided an end-plate side stepped portion formed in such a way that, along a spiral of the wall portion, the height thereof increases toward a central side of the spiral and decreases toward an outer end side thereof; and on the other wall portion of the scrolls, there is provided a wall-portion side stepped portion formed corresponding to the end-plate side stepped portion in such a way that the height thereof decreases toward the central side of the spiral and increases toward the outer end side thereof. In the stated scroll compressor, of a pair of compression chambers facing each other on either side of the center of the stationary scroll, the compression chamber in which the pressure is higher communicates with the discharge port before the compression chamber in which the pressure is lower communicates with the discharge port.

In the case where the end-plate side stepped portion is provided in one of the stationary scroll and the orbiting scroll while the wall-portion side stepped portion is provided in the other of the scrolls, both the scrolls are not formed in the same shape.

Accordingly, the pressures in the pair of compression chambers facing each other on either side of the center of the stationary scroll are not the same. In the present invention, of the pair of compression chambers, the compression chamber in which the pressure is higher is made to communicate with the discharge port before the compression chamber in which the pressure is lower communicates with the discharge port. This makes it possible to avoid the overcompression.

For example, in the case where the end-plate side stepped portion is provided in the orbiting scroll and the wall-portion side stepped portion is provided in the stationary scroll, of the compression chambers facing each other against the wall portion of the stationary scroll, the compression chamber on a ventral side (inner circumferential side) is made to communicate with the discharge port earlier than the other one.

The scroll compressor according to the present invention is provided with a stationary scroll including a spiral wall portion erected on one side surface of an end plate, an orbiting scroll that includes a spiral wall portion erected on one side surface of an end plate and is supported so as to be capable of orbital revolution movement while being prevented from self-rotation by the wall portions being engaged with each other, and a discharge port through which a fluid that has been compressed by both the scrolls is discharged. On the one side surface of the end plate of each of the scrolls, there is provided an end-plate side stepped portion formed in such a way that, along a spiral of the wall portion, the height thereof increases toward a central side of the spiral and decreases toward an outer end side thereof; on the wall portion of each of the scrolls, there is provided a wall-portion side stepped portion formed corresponding to the end-plate side stepped portion in such a way that the height thereof decreases toward the central side of the spiral and increases toward the outer end side thereof; and the heights of the end-plate side stepped portion and the wall-portion side stepped portion corresponding to each other are different. In the stated scroll compressor, of a pair of compression chambers facing each other on either side of the center of the stationary scroll, the compression chamber in which the pressure is higher communicates with the discharge port before the compression chamber in which the pressure is lower communicates with the discharge port.

In the case where the end-plate side stepped portion is formed in each of the stationary scroll and the orbiting scroll, the wall-portion side stepped portion corresponding to the end-plate side stepped portion is formed on the wall portion of each of the stationary scroll and the orbiting scroll, and the heights of the end-plate side stepped portion and the wall-portion side stepped portion corresponding to each other are different, both the scrolls are not formed in the same shape.

Accordingly, the pressures in the pair of compression chambers facing each other on either side of the center of the stationary scroll are not the same. In the present invention, of the pair of compression chambers, the compression chamber in which the pressure is higher is made to communicate with the discharge port before the compression chamber in which the pressure is lower communicates with the discharge port. This makes it possible to avoid the overcompression.

For example, in the case where the end-plate side stepped portion of the orbiting scroll is larger in height than the wall-portion side stepped portion of the stationary scroll, of the compression chambers facing each other against the wall portion of the stationary scroll, the compression chamber on the ventral side (inner circumferential side) is made to communicate with the discharge port earlier than the other one.

The scroll compressor according to the present invention is provided with a stationary scroll including a spiral wall portion erected on one side surface of an end plate, an orbiting scroll that includes a spiral wall portion erected on one side surface of an end plate and is supported so as to be capable of orbital revolution movement while being prevented from self-rotation by the wall portions being engaged with each other, a discharge port through which a fluid that has been compressed by both the scrolls is discharged, and an extraction port for discharging a fluid with a pressure equal to or greater than a predetermined pressure before the fluid being discharged through the discharge port. On the one side surface of the end plate of one of the scrolls, there is provided an end-plate side stepped portion formed in such a way that, along a spiral of the wall portion, the height thereof increases toward a central side of the spiral and decreases toward an outer end side thereof; and on the wall portion of the other of the scrolls, there is provided a wall-portion side stepped portion formed corresponding to the end-plate side stepped portion in such a way that the height thereof decreases toward the central side of the spiral and increases toward the outer end side thereof. In the stated scroll compressor, of a pair of compression chambers facing each other on either side of the center of the stationary scroll, the compression chamber in which the pressure is higher communicates with the extraction port before the compression chamber in which the pressure is lower communicates with the extraction port.

In the case where the end-plate side stepped portion is provided in one of the stationary scroll and the orbiting scroll while the wall-portion side stepped portion is provided in the other of the scrolls, both the scrolls are not formed in the same shape.

Accordingly, the pressures in the pair of compression chambers facing each other on either side of the center of the stationary scroll are not the same. In the present invention, of the pair of compression chambers, the compression chamber in which the pressure is higher is made to communicate with the extraction port (what is called a bypass port) before the compression chamber in which the pressure is lower communicates with the extraction port. This makes it possible to avoid the overcompression.

For example, in the case where the end-plate side stepped portion is provided in the orbiting scroll and the wall-portion side stepped portion is provided in the stationary scroll, of the compression chambers facing each other against the wall portion of the stationary scroll, the compression chamber on the ventral side (inner circumferential side) is made to communicate with the extraction port earlier than the other one.

The scroll compressor according to the present invention is provided with a stationary scroll including a spiral wall portion erected on one side surface of an end plate, an orbiting scroll that includes a spiral wall portion erected on one side surface of an end plate and is supported so as to be capable of orbital revolution movement while being prevented from self-rotation by the wall portions being engaged with each other, a discharge port through which a fluid that has been compressed by both the scrolls is discharged, and an extraction port for discharging a fluid with a pressure equal to or greater than a predetermined pressure before the fluid being discharged through the discharge port. On the one side surface of the end plate of each of the scrolls, there is provided an end-plate side stepped portion formed in such a way that, along a spiral of the wall portion, the height thereof increases toward a central side of the spiral and decreases toward an outer end side thereof; on the wall portion of each of the scrolls, there is provided a wall-portion side stepped portion formed corresponding to the end-plate side stepped portion in such a way that the height thereof decreases toward the central side of the spiral and increases toward the outer end side thereof; and the height of the end-plate side stepped portion and the height of the wall-portion side stepped portion are different. In the stated scroll compressor, of a pair of compression chambers facing each other on either side of the center of the stationary scroll, the compression chamber in which the pressure is higher communicates with the extraction port before the compression chamber in which the pressure is lower communicates with the extraction port.

In the case where the end-plate side stepped portion is formed in each of the stationary scroll and the orbiting scroll, the wall-portion side stepped portion corresponding to the end-plate side stepped portion is formed on the wall portion of each of the stationary scroll and the orbiting scroll, and the heights of the end-plate side stepped portion and the wall-portion side stepped portion corresponding to each other are different, both the scrolls are not formed in the same shape.

Accordingly, the pressures in the pair of compression chambers facing each other on either side of the center of the stationary scroll are not the same. In the present invention, of the pair of compression chambers, the compression chamber in which the pressure is higher is made to communicate with the extraction port (what is called the bypass port) before the compression chamber in which the pressure is lower communicates with the extraction port. This makes it possible to avoid the overcompression.

For example, in the case where the end-plate side stepped portion of the orbiting scroll is larger in height than the wall-portion side stepped portion of the stationary scroll, of the compression chambers facing each other against the wall portion of the stationary scroll, the compression chamber on the ventral side (inner circumferential side) is made to communicate with the discharge port earlier than the other one.

Advantageous Effects of Invention

The overcompression can be prevented because the compression chamber in which the pressure is higher is made to communicate with the discharge port or the extraction port earlier than the other one.

DESCRIPTION OF EMBODIMENTS

First Embodiment

A first embodiment of the present invention will be described below, usingFIGS. 1 to 5 and 9.

As illustrated inFIG. 1, a scroll compressor1includes a housing2constituting an outline. This housing2is a cylinder with an open front end side (left side in the drawing) and a sealed rear end side. By fastening and fixing a front housing3into the opening on the front end side using bolts4, a sealed space is formed in the interior of the housing2, and a scroll compression mechanism5and a drive shaft6are incorporated in the sealed space.

The drive shaft6is rotatably supported by the front housing3via a main bearing7and an auxiliary bearing8. A pulley11, which is rotatably provided on an outer circumferential portion of the front housing3via a bearing10, is connected, via an electromagnetic clutch12, to a front end portion of the drive shaft6, which protrudes to the outside from the front housing3via a mechanical seal9, such that motive power from outside can be transmitted. A crank pin13, which is eccentric by a predetermined dimension, is integrally provided on the rear end of the drive shaft6, and is connected to an orbiting scroll16of the scroll compression mechanism5described below, via a known slave crank mechanism14that includes a drive bushing having a variable turn radius and a drive bearing.

In the scroll compression mechanism5, a pair of compression chambers17, facing each other on either side of the center of a stationary scroll15, are formed between the stationary scroll15and the orbiting scroll16, as a result of a pair of the stationary and orbiting scrolls15and16being engaged with each other with a 180 degrees phase difference. The scroll compression mechanism5is configured to compress a fluid (a refrigerant gas) by moving each of the compression chambers17from an outer circumferential position to a center position while gradually reducing the capacity thereof.

A discharge port18, which discharges compressed gas, is provided in a center section of the stationary scroll15, and the stationary scroll15is fixedly provided on a bottom wall surface of the housing2via bolts19. Further, the orbiting scroll16is connected to the crank pin13of the drive shaft6via the slave crank mechanism14, and is supported by a thrust bearing surface of the front housing3, via a known self-rotation prevention mechanism20, such that the orbiting scroll16is freely capable of orbital revolution drive.

An O-ring21is provided around the outer circumference of an end plate15A of the stationary scroll15. As a result of the O-ring21making close contact with the inner circumferential surface of the housing2, the internal space of the housing2is partitioned into a discharge chamber22and an intake chamber23. The discharge port18opens into the discharge chamber22. The compressed gas from the compression chambers17is discharged through the discharge port18, and then discharged to a refrigeration cycle side therefrom.

Further, an intake port24, which is provided in the housing2, opens into the intake chamber23. A low-pressure gas, which has circulated through the refrigeration cycle, is taken into the intake port24, and then, the refrigerant gas is taken into the interior of the compression chambers17via the intake chamber23.

Further, the pair of the stationary scroll15and the orbiting scroll16includes spiral wraps15B and16B disposed as wall portions in an upright manner on the end plate15A and an end plate16A, respectively. A tooth crest15C of the stationary scroll15makes contact with a tooth base16D of the orbiting scroll16, and a tooth crest16C of the orbiting scroll16makes contact with a tooth base15D of the stationary scroll15.

On the end plate16A of the orbiting scroll16, there is provided an end-plate side stepped portion16E formed in such a way that, along a spiral of the spiral wrap16B, the height thereof increases toward a central side of the spiral and decreases toward an outer end side thereof. To be specific, as illustrated inFIG. 2, the end-plate side stepped portion16E is provided at a position of 180 degrees apart from a wrapping end position of the spiral wrap16B of the orbiting scroll16.

On the spiral wrap15B of the stationary scroll15, there is provided a wrap side stepped portion15E corresponding to the end-plate side stepped portion16E of the orbiting scroll16in such a way that the height thereof decreases toward the central side of the spiral and increases toward the outer end side thereof. To be specific, as illustrated inFIG. 2, the wrap side stepped portion15E is provided at a position of 360 degrees apart from the wrapping end position of the spiral wrap15B of the stationary scroll15.

In other words, the end-plate side stepped portion16E is provided only on the end plate16A of the orbiting scroll16, and the wrap side stepped portion15E is provided only on the spiral wrap15B of the stationary scroll15. Accordingly, no stepped portion is provided on the spiral wrap16B of the orbiting scroll16, and a tip end of the spiral wrap16B is leveled in height. Further, no stepped portion is provided on the end plate15A of the stationary scroll15so as for the end plate15A thereof to have a flat surface.

FIG. 9includes the stationary scroll15provided with an end-plate side stepped portion having a height lower than the end-plate side stepped portion16E of the orbiting scroll16, with respect toFIG. 1.FIG. 9further includes an end plate side stepped portion15G provided on the stationary scroll15, and a wrap side stepped portion16G provided on the orbiting scroll16.

As illustrated inFIG. 2, the compression chambers17are formed of at least a pair of compression chambers17A and17B facing each other on either side of the center of the stationary scroll15. InFIG. 2, in order to distinguish the pair of compression chambers17A and17B, the compression chamber formed on a ventral side (inner circumferential side) of the spiral wrap15B of the stationary scroll15is defined as a ventral side compression chamber17A while the compression chamber formed on a dorsal side (outer circumferential side) of the spiral wrap15B of the stationary scroll15is defined as a dorsal side compression chamber17B.

FIG. 3shows changes in capacity of the ventral side compression chamber17A and the dorsal side compression chamber17B. In the graph, the horizontal axis represents a swivel angle θ*, and the vertical axis represents the capacity of the compression chambers17A and17B.

As can be understood fromFIG. 3, after a pair of compression chambers is formed on the outermost circumferential side when the intake is ended at a swivel angle α1, the compression is performed from the above swivel angle, with the ventral side compression chamber17A and the dorsal side compression chamber17B having different capacity, up to a swivel angle α2, which is a swivel angle at which the ventral side and dorsal side compression chambers17A and17B have the same capacity and the fluid is discharged. Because a change rate (slant) of the capacity of the ventral side compression chamber17A is larger than that of the dorsal side compression chamber17B, the pressure in the ventral side compression chamber17A becomes higher than that in the dorsal side compression chamber17B, which raises a risk that an excessive discharge pressure may be brought about in the ventral side compression chamber17A.

As such, in the present embodiment, as illustrated inFIGS. 4A and 4B, a shape of the discharge port18is adjusted so that the ventral side compression chamber17A communicates with the discharge port18earlier than the dorsal side compression chamber17B. As a method for adjusting the shape of the discharge port18, it is sufficient that the discharge port18has a larger diameter than a diameter of a discharge port18′ adjusted so that the ventral side compression chamber17A and the dorsal side compression chamber17B open at the same time.

Positions a and b illustrated in the drawings indicate communication start points of the ventral side compression chamber17A and the dorsal side compression chamber17B, respectively, in a case of using the discharge port18′ adjusted so that the ventral side compression chamber17A and the dorsal side compression chamber17B open at the same time. As can be understood from the drawings, with the discharge port18having a larger diameter than the diameter of the discharge port18′ adjusted so that the ventral side compression chamber17A and the dorsal side compression chamber17B open at the same time, the ventral side compression chamber17A communicates with the discharge port18earlier than the dorsal side compression chamber17B.

As another method for adjusting the shape of the discharge port18, as illustrated inFIG. 4C, the discharge port18may have the same diameter as that of the discharge port18′ adjusted so that the ventral side compression chamber17A and the dorsal side compression chamber17B open at the same time, and a center position thereof may be moved toward the ventral side compression chamber17A side, that is, toward an outer side (left side in the drawing) of the wrapping of the spiral wrap15B of the stationary scroll15. Alternatively, a cross section of the discharge port18may not have a circular shape but have a shape such as an elliptical shape or a keyhole shape, so that the discharge port18may communicate earlier with the ventral side compression chamber17A.

According to the scroll compressor1of the present embodiment, it is possible to obtain the following effects.

Of the pair of the compression chambers17A and17B facing each other on either side of the center of the stationary scroll15, the ventral side compression chamber17A in which the pressure is higher is made to communicate with the discharge port earlier than the dorsal side compression chamber17B in which the pressure is lower.

With this, even if the scroll compressor1is configured such that the stepped portion16E is provided on the end plate16A of the orbiting scroll16, the stepped portion15E corresponding to the stepped portion16E is provided on the spiral wrap15B of the other scroll, that is, the stationary scroll15, and the pressures in the pair of the compression chambers17A and17B facing each other on either side of the center of the stationary scroll15are not the same, thus, the overcompression of the ventral side compression chamber17A can be avoided.

To be specific, as shown inFIG. 5, because the ventral side compression chamber17A communicates with the discharge port18at a swivel angle α3before a swivel angle α4at which the dorsal side compression chamber17B communicates with the discharge port18, the ventral side compression chamber17A is not further compressed after the swivel angle α3. With this, it can be avoided that energy corresponding to a substantially triangular region A1shown inFIG. 5becomes motive power loss and reduces the compression efficiency.

The description of the present embodiment is given using the configuration in which the end-plate side stepped portion16E is provided only on the end plate16A of the orbiting scroll16, and the wrap side stepped portion15E is provided only on the spiral wrap15B of the stationary scroll15. However, a configuration in which the above constituent elements are provided in a reversed manner may be used.

In other words, the present invention can be also applied to the configuration in which the end-plate side stepped portion is provided only on the end plate15A of the stationary scroll15, and the wrap side stepped portion is provided only on the spiral wrap16B of the orbiting scroll16.

In this case, because the pressure in the dorsal side compression chamber17B becomes higher than that in the ventral side compression chamber17A, the configuration should be such that the dorsal side compression chamber17B communicates with the discharge port18earlier than the ventral side compression chamber17A. For example, inFIG. 4A, a notch, a groove, or the like is provided on the ventral side of the spiral wrap16B of the orbiting scroll16so that a gap is generated earlier at the position b.

The present invention can be also applied to a scroll compressor in which end-plate side stepped portions are provided on end plates of both a stationary scroll and an orbiting scroll as explained using Patent Literature 1.

That is, in the case where the height of the end-plate side stepped portion provided on the end plate of the orbiting scroll is larger than that of the end-plate side stepped portion provided on the end plate of the stationary scroll, because, like in the present embodiment, the pressure in the ventral side compression chamber17A becomes higher than that in the dorsal side compression chamber17B, adjusting the shape of the discharge port makes it possible to avoid the overcompression of the ventral side compression chamber17A.

On the other hand, in the case where the height of the end-plate side stepped portion provided on the end plate of the stationary scroll is larger than that of the end-plate side stepped portion provided on the end plate of the orbiting scroll, because the pressure in the dorsal side compression chamber17B becomes higher than that in the ventral side compression chamber17A, providing a notch, a groove, or the like on the ventral side of the spiral wrap16B of the orbiting scroll16makes it possible to avoid the overcompression of the dorsal side compression chamber17B.

Second Embodiment

Next, a second embodiment of the present invention will be described with reference toFIG. 6AtoFIG. 8.

The present embodiment differs from the first embodiment in a point that a bypass port is provided in addition to the configuration of the first embodiment. As such, same configurations as those in the first embodiment are given the same reference signs, and explanations thereof are omitted.

A scroll compressor1of the present embodiment has a vertical cross-sectional shape as illustrated inFIG. 1. In addition, in the scroll compressor1of the present embodiment, as illustrated inFIGS. 6A and 6B, bypass ports (extraction ports)30A and30B are formed in the end plate15A of the stationary scroll15. The bypass ports30A and30B each include a check valve or the like, where the valve opens when the pressure becomes equal to or greater than a predetermined one. A fluid with a pressure equal to or greater than the predetermined one is discharged through the bypass ports before the fluid is discharged through the discharge port18, thereby avoiding the overcompression. InFIGS. 6A and 6B, one bypass port30A corresponds to the ventral side compression chamber17A, and the other bypass port, that is, the bypass port30B corresponds to the dorsal side compression chamber17B.

In the present embodiment, as illustrated inFIG. 6A, at a swivel angle β1, the ventral side compression chamber17A communicates with the bypass port30A while the dorsal side compression chamber17B does not communicate with the bypass port30B. Accordingly, at the swivel angle β1, an amount of fluid corresponding to an excessive pressure is extracted only from the ventral side compression chamber17A. Then, as illustrated inFIG. 6B, when having advanced to a swivel angle β2, the dorsal side compression chamber17B communicates with the bypass port30B. At the swivel angle β2, the ventral side compression chamber17A has already communicated with the bypass port30A.

FIGS. 7A and 7Billustrate communication start timings of the bypass ports as a comparative example. The configuration of this comparative example corresponds to a case in which a pressure differential between the ventral side compression chamber17A and the dorsal side compression chamber17B is substantially zero, or is small so as not to affect the performance. As illustrated inFIG. 7A, none of the bypass ports30A and30B communicate with the compression chambers17A and17B at the swivel angle β1; as illustrated inFIG. 7B, at the swivel angle β2, the compression chambers17A and17B communicate with the bypass ports30A and30B at the same time.

FIG. 8shows pressure changes due to the bypass ports30A and30B of the present embodiment illustrated inFIGS. 6A and 6B. In the graph, the horizontal axis represents the swivel angle, and the vertical axis represents the pressure. As can be understood from the graph, the pressure in the ventral side compression chamber17A becomes higher than that in the dorsal side compression chamber17B from around a swivel angle β0.

Then, as illustrated inFIG. 6A, at the swivel angle β1, the ventral side compression chamber17A starts communicating with the bypass port30A, and is not excessively compressed to a pressure equal to or greater than a requested discharge pressure. Thereafter, as illustrated inFIG. 6B, at the swivel angle β2, the dorsal side compression chamber17B starts communicating with the bypass port30B, and is adjusted to the requested discharge pressure until at a swivel angle β3at which the compression chamber communicates with the discharge port18.

In contrast, in the case where both the compression chambers17A and17B start communicating with the bypass ports30A and30B at the same time at the swivel angle β2, as illustrated inFIGS. 7A and 7B, the ventral side compression chamber17A is excessively compressed to a pressure equal to or greater than the requested discharge pressure as shown inFIG. 8. Accordingly, energy corresponding to a substantially triangular region A2shown inFIG. 8becomes motive power loss and reduces the compression efficiency.

According to the scroll compressor1of the present embodiment, it is possible to obtain the following effects.

Of the pair of the compression chambers17A and17B facing each other on either side of the center of the stationary scroll15, the ventral side compression chamber17A in which the pressure is higher is made to communicate with the bypass port30A earlier than the dorsal side compression chamber17B in which the pressure is lower.

With this, even if the scroll compressor1is configured such that the stepped portion16E is provided on the end plate16A of the orbiting scroll16, the spiral wrap15B of the other scroll, that is, the stationary scroll15includes a shape of the stepped portion15E corresponding to the stepped portion16E, and the pressures in the pair of the compression chambers17A and17B facing each other on either side of the center of the stationary scroll15are not the same, the overcompression of the ventral side compression chamber17A can be avoided.

In the present embodiment, such a configuration is assumed that the end-plate side stepped portion16E is provided only on the end plate16A of the orbiting scroll16, and the wrap side stepped portion15E is provided only on the spiral wrap15B of the stationary scroll15. However, a configuration in which the above constituent elements are provided in a reversed manner may be employed.

In other words, the present invention can be also applied to the configuration in which the end-plate side stepped portion is provided only on the end plate15A of the stationary scroll15, and the wrap side stepped portion is provided only on the spiral wrap16B of the orbiting scroll16.

In this case, because the pressure in the dorsal side compression chamber17B becomes higher than that in the ventral side compression chamber17A, the position of the bypass port30B is adjusted so that the dorsal side compression chamber17B communicates with the bypass port30B earlier than the ventral side compression chamber17A.

The present invention can be also applied to a scroll compressor in which end-plate side stepped portions are provided on end plates of both a stationary scroll and an orbiting scroll as explained using Patent Literature 1.

That is, in the case where the height of the end-plate side stepped portion provided on the end plate of the orbiting scroll is larger than that of the end-plate side stepped portion provided on the end plate of the stationary scroll, because, like in the present embodiment, the pressure in the ventral side compression chamber17A becomes higher than that in the dorsal side compression chamber17B, adjusting the position of the bypass port30A makes it possible to avoid the overcompression of the ventral side compression chamber17A.

On the other hand, in the case where the height of the end-plate side stepped portion provided on the end plate of the stationary scroll is larger than that of the end-plate side stepped portion provided on the end plate of the orbiting scroll, because the pressure in the dorsal side compression chamber17B becomes higher than that in the ventral side compression chamber17A, adjusting the position of the bypass port30B makes it possible to avoid the overcompression of the dorsal side compression chamber17B.

REFERENCE SIGNS LIST