COMBINED COMPRESSING APPARATUS

Abstract

In a scroll compressor, a fixed wrap of a fixed end plate engages with an orbiting wrap of an orbiting plate to form a compressing chamber. A gas is introduced into the compressing chamber from the outer circumference and compressed towards the center as the orbiting end plate revolves with a driving shaft with respect to the fixed end plate. The gas is sent to a reciprocating compressor in which a piston moves up and down in a cylinder and further compressed therein.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a combined compressing apparatus compressing in a downstream compressor a compressed gas discharged from an upstream compressor.

JP2703319B2 discloses a combined compressing apparatus in which a turbo-type compressor is used as an upstream compressor and a volume-type compressor such as a reciprocating compressor or a scroll compressor is used as a downstream compressor. A primary compressed gas in the turbo-type compressor is forwarded to the volume-type compressor in which a primary compressed gas is further compressed and discharged as a secondary high-pressure compressed gas.

However, in a known combined compressing apparatus, a massive low-pressure compressed gas is discharged from the turbo-type compressor as upstream compressor, so that a large volume-type compressor is used to suck the primary massive compressed gas from the turbo-type compressor to make its size larger and make power load increased.

SUMMARY OF THE INVENTION

In view of the disadvantages in the prior art, it is an object of the invention to provide a combined compressing apparatus which makes its size smaller and makes power load decreased thereby producing a high-pressure compressed gas effectively.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the invention will become more apparent from the following description with respect to embodiments as shown in accompanying drawings wherein:

FIG. 1 is a schematic view of a combined compressing apparatus according to the present invention;

FIG. 2 is a vertical sectional view of the first embodiment of a combined compressing apparatus according to the present invention; and

FIG. 3 is a vertical sectional view of the second embodiment of a combined compressing apparatus according to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

As shown in FIG. 1, in a combined compressor according to the present invention, a scroll compressor 1 that is excellent in quietness and saving energy is employed as upstream compressor and a reciprocating compressor 2 that is simple in structure and can supply high pressure is employed as downstream compressor. A primary compressed gas A compressed by the scroll compressor 1 is sent to the reciprocating compressor 2, by which the primary compressed gas A is further compressed to a high pressure secondary compressed gas B which is sent to a tank 3.

In FIG. 2, the first embodiment of a combined compressing apparatus is shown in which the rear of a cylindrical housing 11 of the scroll compressor 1 is fixed to the front of a crank case 22 of the reciprocating compressor 2. A single motor 4 is mounted to the rear of the crank case 22. The motor 4 acts as power source for driving the scroll compressor 1 and the reciprocating compressor 2.

The scroll compressor 1 comprises an involute fixed wrap 13 in the sealed housing 11 and an orbiting wrap 15 which engages with the fixed wrap 13 to form a compressing chamber 16.

The fixed wrap 13 is provided on the rear surface of a fixed end plate 12, while the orbiting wrap 15 is provided on an orbiting plate 14 rotatably mounted in the housing 11.

The orbiting plate 14 is rotatably mounted to an eccentric axial portion 42 of a driving shaft 41 which passes through a center of a cover 24 closing the rear surface of the housing 11 and is rotated by a motor 4. The cover 24 is also part of the crank case 22 of the reciprocating compressor 2. The orbiting plate 14 is eccentrically revolved with rotation of the driving shaft 41 and connected to the cover 24 with three pin-crank-type self-rotation preventing devices 17 positioned on a circle.

In the outer circumference and center of the fixed end plate 12 of the housing 11, there are a scroll inlet 111 for sucking an external gas into the compressing chamber 16 and a scroll outlet 112 for discharging a primary compressed gas A compressed in the compressing chamber 16 respectively.

When the orbiting end plate 14 is eccentrically revolved by the motor 4, the compressing chamber 16 defined by the fixed wrap 13 and the orbiting wrap 15 gradually reduces in volume from the outer circumference to the center. Thus, the external gas sucked from the scroll inlet 111 is gradually compressed towards the center and the primary compressed gas A is discharged from the scroll outlet 112. The primary compressed gas A from the scroll outlet 112 is forwarded to the reciprocating compressor 2 and partially introduced into the crank case 22 of the reciprocating compressor 2.

In the reciprocating compressor 2, a piston 23 reciprocates in a cylinder 21 to suck and discharge a gas over and over. On the cylinder 23, there are a cylinder inlet 25 for introducing the primary compressed gas A discharged from the scroll outlet 112 into the cylinder 21 and a cylinder outlet 26 for discharging a secondary compressed gas B compressed in the cylinder 21.

The piston 23 is reciprocated in the cylinder 21 with a crank shaft 43 of the driving shaft 41 driven by the motor 4 via a piston rod 27.

In the upper part of the crank case 22, there is a crank-case inlet 221 for partially sucking the primary compressed gas A discharged from the scroll outlet 112 into the crank case 22.

The piston 23 reciprocates in the cylinder 21, so that the primary compressed gas A is introduced from the cylinder inlet 25 via a suction valve 28 over the piston 23 in the cylinder 21 and further compressed. Then, high-pressure secondary compressed gas B is discharged from the cylinder outlet 26 via a discharge valve 26 and sent to the tank 3.

During reciprocating motion of the piston 23, the primary compressed gas A discharged from the scroll outlet 112 of the scroll compressor 1 is partially introduced into the crank case 22 to allow the inside of the crank case 22 to be pressured to more than atmospheric pressure. Thus, difference in pressure between the compressed gas in the compressing chamber on the piston 23 and that in the crank case 22 is smaller than what has about atmospheric pressure in the crank case 22. Therefore, if difference in pressure between the upper surface and lower surfaces of the piston 23 is great, rapid and strong downward force acts onto the piston 23, so that excessive and unequal force is applied to the outer circumferential surface of the piston 23, the piston ring, a bearing and a sealing portion thereby causing early malfunction. In the embodiment of the present invention, difference in pressure becomes smaller to avoid the cause of early malfunction thereby discharging smaller high-pressure compressed gas efficiently.

In the first embodiment, the primary compressed gas A compressed in the scroll compressor 1 excellent in quietness and energy saving is further compressed in the reciprocating compressor 2 which is simple in structure and possesses high-pressure availability to allow the secondary high-pressure compressed gas B to be discharged. The scroll compressor 1 is driven together with the reciprocating compressor 2 by the single motor 4, thereby reducing size and saving cost. Furthermore, as mentioned above, the primary compressed gas A discharged from the scroll outlet 112 of the scroll compressor 1 is partially introduced into the crank case 22 thereby reducing size of the reciprocating compressor 2 and improving quietness.

In the second embodiment of a combined compressing apparatus in FIG. 3, a scroll compressor 1 and a reciprocating compressor 3 comprise motors 4,5 respectively as power source. On the way of a fluid path through which a primary compressed gas A compressed in the scroll compressor 1 is forwarded to a cylinder inlet 25 of the reciprocating compressor 2, a selector valve 6 is provided. Except them, it is similar to those in the first embodiment. The same numerals are allotted to the same members as those in the first embodiment and its description is omitted.

A motor 5 for driving the scroll compressor 1 is mounted in front of a sealed cylindrical housing 11. An orbiting plate 14 having an orbiting wrap 15 is rotatably mounted to an eccentric axial portion 52 of a driving shaft 51 driven by a motor 5 and going through the center of a cover 18 of the housing 11, and connected to the cover 18 via a pin-crank-type self-rotation preventing device 17 to eccentrically revolve with rotation of the driving shaft 51.

On the upper part of the housing 11 and through the center of the fixed end plate 12, there are a scroll inlet 111A for sucking an external gas into the compressing chamber 16 and a scroll outlet 112A for discharging a primary compressed gas compressed by the compressing chamber 16 to introduce it into a crank case 22 of the reciprocating compressor 2.

The primary compressed gas A discharged from the scroll outlet 112A is introduced into the crank case 22 through a through hole 44 extending axially towards the end of the driving shaft 41 of the motor 4.

On the upper part of the crank case 22, there is formed a crank-case outlet 222 for discharging the primary compressed gas A introduced into the crank case 22 and forwarding it into the cylinder inlet 25.

A selector valve 6 is provided on the way of the fluid path between the crank-case outlet 222 and the cylinder inlet 25 to enable the selector valve 6 to be switched to a first fluid path 9 for forwarding the primary compressed gas A discharged from the crank-case outlet 222 to the cylinder inlet 25 or to a second fluid path 10 for forwarding it to a downstream side of the cylinder outlet 26, going around the reciprocating compressor 2.

The selector valve 6 is switched by a control device 7 having an electric circuit, and the motors 4,5 are driven, stopped and controlled by the control device 7. A pressure sensor 8 for measuring pressure in a tank 3 is provided at the downstream side of the cylinder outlet 26. Information such as measured value by the pressure sensor 8 is transmitted to the control device 7 which stops when compressed gas in the tank 3 reduces in consumed amount to allow compressed gas forwarded to the tank 3 to increase.

To require a secondary high-pressure compressed gas B, a switch (not shown) for the control device 7 is switched to a high-pressure side. Thus, the first fluid path 9 of the selector valve 6 is opened, while the second fluid path 10 is closed thereby allowing the motors 4,5 to be driven together.

As a result, the scroll compressor 1 and reciprocating compressor 2 are both actuated, so that the primary compressed gas A compressed in the scroll compressor 1 is introduced into the crank case 22 through the scroll outlet 112A and the through hole 44 and discharged from the crank-case outlet 222.

The primary compressed gas A from the crank-case outlet 222 is forwarded to the cylinder inlet 25 through the selector valve 6 and the first fluid path 9 and introduced into the cylinder 21. Thus, the secondary high-pressure compressed gas B is discharged from the cylinder outlet 26.

To require a primary low-pressure compressed gas A, the switch of the control device 7 is switched to a low-pressure side. Thus, a solenoid 61 of the selector valve 6 is magnetized to close the first fluid path 9 of the selector valve 6 and to open the second fluid path 10 and drives only the motor 5. As a result, the scroll compressor 1 is only operated, so that a primary compressed gas A compressed in the scroll compressor 1 is introduced into the crank case 22 through the scroll outlet 112A and the through hole 44 and is discharged from the crank-case outlet 222. And the primary compressed gas A discharged from the crank-case outlet 222 is not forwarded to the cylinder inlet 25, but is forwarded to the downstream side of the cylinder outlet 26 through the selector valve 6 and the second fluid path 10.

In the second embodiment, the secondary high-pressure compressed gas can be effectively obtained similar to the first embodiment. The primary compressed gas A compressed in the scroll compressor 1 is introduced into the crank case 22 thereby allowing the reciprocating compressor 2 to become smaller and improving quietness. Also, by switching the selector valve 6, the primary low-pressure compressed gas A and the secondary compressed gas B can be selectively obtained if required. Especially, when the primary low-pressure compressed gas A is required, the reciprocating compressor 2 stops to let the scroll compressor 1 driven only thereby improving quietness and energy saving.

The embodiments of the present invention are described and the following changes and modifications may be made without departing from the scope of claims below.

• • (i) The primary compressed gas A compressed and discharged in the scroll compressor 1 in the first embodiment is directly introduced into the crank case 22 of the reciprocating compressor 2 as described in the second embodiment. And the primary compressed gas A introduced in the crank case 22 is discharged from the crank case 22 and forwarded to the cylinder inlet 25.
  • (ii) The primary compressed gas A compressed in and discharged from the scroll compressor 1 in the second embodiment is partially introduced into the crank case 22 of the reciprocating compressor as described in the first embodiment.
  • (iii) In the second embodiment, the selector valve 6 allows the first fluid path 9 to close and the second fluid path 10 to open based on a measured value higher than a certain value by the pressure sensor 8 measuring pressure in the tank 6 storing the secondary compressed gas B discharged from the cylinder outlet 26 of the reciprocating compressor 2, while the selector valve 6 allows the first fluid path 9 to open and the second fluid path 10 to close based on a measured value lower than a certain value by the pressure sensor 8.

Claims

1. A combined compressing apparatus comprising:

a scroll compressor comprising a driving shaft, a fixed end plate and an orbiting plate rotatably mounted to the driving shaft, a fixed wrap of the fixed end plate engaging with an orbiting wrap of the orbiting end plate to form a compressing chamber, the orbiting plate that revolves with respect to the fixed end plate with rotation of the driving shaft compressing a gas introduced through a scroll inlet in the outer circumference of the fixed end plate towards a center to discharge a primary compressed gas through a scroll outlet at the center; and

a reciprocating compressor comprising a cylinder and a piston moving up and down in the cylinder, said cylinder having a cylinder inlet and a cylinder outlet, the cylinder inlet being connected to the scroll outlet to enable the primary compressed gas to be introduced into the cylinder and to be compressed by reciprocating the piston in the cylinder.

2. A combined compressing apparatus of claim 1 wherein the reciprocating compressor further comprises a crank case, a piston rod mounted to a lower surface of the piston in the crank case and a crank shaft connected to a lower part of the piston rod in the crank case.

3. A combined compressing apparatus of claim 2 wherein the scroll compressor and the reciprocating compressor are driven by a single power source.

4. A combined compressing apparatus of claim 3 wherein the power source comprises a motor.

5. A combined compressing apparatus of claim 2 wherein the scroll outlet is also connected to a crank-case inlet of the crank case to allow the primary compressed gas to be introduced into the crank case to increase internal pressure in the crank case.

6. A combined compressing apparatus of claim 3 wherein the driving shaft that drives the orbiting plate is connected to the crank shaft of the reciprocating compressor to allow the scroll and reciprocating compressors to be driven together.

7. A combined compressing apparatus of claim 1 wherein the scroll compressor and the reciprocating compressor are driven by first and second power sources respectively.

8. A combined compressing apparatus of claim 7 wherein the power source comprises a motor.

9. A combined compressing apparatus of claim 7, further comprising a selector valve on a flow path of the primary compressed gas from the scroll compressor to the reciprocating compressor to switch whether the primary compressed gas goes to the reciprocating compressor or is directly discharged without going to the reciprocating compressor.

10. A combined compressing apparatus of claim 9, further comprising a control device connected to the selector valve to switch whether or not the primary compressed gas should be sent to the reciprocating compressor.

11. A combined compressing apparatus of claim 10, further comprising a tank that receives finally compressed gas and a pressure sensor that measures pressure in the tank, said pressure sensor being connected to the control device to send the control device information of the pressure in the tank to decide whether or not the primary compressed gas should be further compressed in the reciprocating compressor.

12. A combined compressing apparatus of claim 8 wherein the scroll compressor communicates with the crank case through a though hole along a central axis of the scroll compressor.

13. A combined compressing apparatus of claim 10 wherein the control device is connected to the first power source and the second power source when one of the scroll an reciprocating compressors is required to stop by stopping one of the first and second power sources connected to the scroll and reciprocating compressors.