JPH0260873B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a scroll fluid machine used as a refrigerant compressor or an air compressor for refrigeration and air conditioning.

[Conventional technology]

Taking a scroll fluid machine as an example of an air compressor,
The basic configuration of the prior art will be explained with reference to FIGS. 1 and 2.

Reference numeral 1 designates a fixed scroll having a spiral wrap portion 1b standing upright on a flat plate portion 1b. Reference numeral 2 designates an orbiting scroll having a spiral wrap portion 2b standing upright on an end plate 2a. The fixed scroll 1 and the orbiting scroll 2 are engaged with each other with their laps facing inward and outward, and the orbiting scroll 2 is the fixed scroll 1.
and an outer frame 9 fixed to the fixed scroll 1. Further, a turning means called an Oldham mechanism is formed between the outer frame 9 and the turning scroll 2, and includes an Oldham key 3, an Oldham ring 4, etc. The scroll 2 performs a turning motion without rotating. When the crankshaft 12 rotates clockwise and the orbiting scroll 2 rotates clockwise, the intake air is sucked into the compressor through the suction filter 14, the suction pipe 18, and the suction port 1c, and is drawn into the suction chamber on the outer periphery of the wrap. Among the compressors formed by the fixed scroll 1 and the orbiting scroll 2, the compressor 5a located at the outermost position gradually decreases in volume with the orbiting motion, moving towards the center of

When both compressors 5a reach the vicinity of the centers of both scrolls 1 and 2, both compressors 5a communicate with the discharge port 1d, and the compressed gas is discharged.

However, due to the compressive action between the fixed scroll 1 and the orbiting scroll 2, an axial gas force is generated between the scrolls that tends to pull them apart in the main axis direction. When both scrolls are separated by pressure, the flat plate portions 1a and 2b of the wraps 1b and 2b
The seal between the end face in the axial direction with the end plate 2a becomes incomplete, gas leakage increases, and efficiency decreases.
For this reason, normally, on the back of the orbiting scroll 2,
Applying an axial pressing force by a mechanical method such as a spring, or from a place having a certain pressure source 15 as described in Japanese Patent Application Laid-Open No. 117304/1982,
Through the pressure introduction pipe 16 via the on-off valve 15a,
Gas pressure is introduced into the back pressure chamber 35 to balance the axial gas force due to the internal pressure described above.
17 is a pressure introduction hole, 6, 7, 8 are bearings, 1
0 is a pressure sealing means, 11 is a seal cover, 13
indicates balance weight.

In addition, as another measure for applying back pressure, for example, as shown in Japanese Patent Laid-Open No. 55-37520, a small hole is provided in the end plate of the orbiting scroll, and the gas pressure during compression is passed through the small hole. There is something that leads to the back pressure chamber.

[Problem to be solved by the invention]

Now here, the axial gas force is Fa due to the internal pressure.
The axial pressing force due to the pressure inside the back pressure chamber 35 is
Assuming Fb, a thrust force force Rs such as Fs=Fb-Fa is generally applied from the orbiting scroll 2 to the axial sliding surface of the fixed scroll 1. Showa 55
- In the method for applying back pressure in Publication No. 37520, an appropriate back pressure chamber pressure value is applied during steady operation at a constant rotation speed and neither discharge pressure nor suction pressure changes, but when starting up or at low speed rotation. When the suction pressure decreases, such as when moving, an excessive backpressure that is approximately twice as high as the appropriate backpressure is generated. When the back pressure in the back pressure chamber increases abnormally during these unsteady operations, the thrust force Fs also increases, causing the sliding surface on the outer circumference of the fixed scroll flat plate portion 1a and the tips of the scroll laps 1b and 2b to This increases dynamic friction loss, reduces mechanical efficiency, and causes adhesive wear on sliding surfaces, which tends to reduce the reliability of the compressor.

In the conventional method described above, in order to eliminate an excessive back pressure chamber pressure value, it is necessary to control both the pressure of the pressure source and the on-off valve.

The present invention was invented in view of the above-mentioned problems, and it is an object of the present invention to prevent compressor damage caused by an abnormal increase in back pressure when the suction pressure decreases, which frequently occurs, with a simple structure.

[Means to solve the problem]

The above purpose is to release the excess pressure to the suction passage through a valve device that operates against the excess pressure when the pressure in the back pressure chamber becomes excessive during unsteady operation. This is achieved by connecting the back pressure chamber and the suction path.

[Effect]

If the back pressure in the back pressure chamber exceeds the appropriate value and becomes excessive, especially during unsteady operation such as when starting the scroll or transitioning to low-speed rotation due to a drop in suction pressure, the valve device will Excess backpressure flows through the suction passage very quickly. As a result, even if the operating conditions change, the pressure in the back pressure chamber will not increase abnormally.

〔Example〕

An embodiment of the present invention will be described based on FIGS. 3 and 4. FIG. 3 shows an embodiment in which a scroll fluid machine is used as an air compressor. In the figure, the same parts as in FIG. 1 are designated by the same reference numerals, and the explanation thereof will be omitted.

From the back pressure pressure source 15 fluid supply section, a pressure introduction pipe 16 with a solenoid valve 15a interposed as an on-off valve is connected.
It is connected to the pressure introduction hole 17 of the outer frame 9 and opens into the back pressure chamber 35 . Note that the pressure source, ie, the fluid supply section, may be provided by the method described in Japanese Patent Application Laid-Open No. 55-37520. A discharge pipe 19 with a check valve 19a interposed therebetween is connected to the discharge port 1d, and the other end is connected to a pressure tank 20. A high pressure switch 21 is installed in this pressure tank 20. In addition, instead of the pressure source 15, a conduit is branched from the discharge pipe 19 (not shown), and a part of the high-pressure gas is branched and reduced in pressure by a throttle valve (not shown), etc., and then sent to the back pressure chamber 35. It may be allowed to flow in. Further, a suction pipe 18 from a suction filter 14 is connected to the suction port 1c provided in the fixed scroll 1, and the back pressure chamber 35 and the suction pipe 18 are controlled by a throttle valve or an on-off valve, etc. They are connected by a bypass pipe 24 with a means 23 interposed therebetween. 22 is a back pressure relief hole, 2
5 indicates a back pressure inflow hole. Other parts are similar to the conventional example shown in FIG.

The intake air is passed through the intake filter 14 and the intake pipe 1.
8 to the compression element and communicates with the suction chamber 40 through the suction port 1c provided in the fixed scroll 1.
Compression is performed by both scrolls 1 and 2 in the same way as in the conventional example, and the discharged gas becomes high temperature and high pressure.
It is discharged from the discharge port 1d of the fixed scroll 1 through the discharge pipe 19 into the pressure tank 20. Discharge pipe 19
A check valve 19a is provided in the middle to prevent backflow from the pressure tank to the compressor when the compressor is stopped.

The operation of the scroll compressor having the above structure will be explained.

A case will be described in which a solenoid valve 23a is used as the control means 23. During steady operation in which the pump is operated at a constant rotational speed and neither the discharge pressure nor the suction pressure changes, an appropriate back pressure chamber pressure is applied to the back pressure chamber from the pressure source 15 (fluid supply section). During unsteady operation such as when starting up a scroll fluid machine or transitioning to low speed rotation,
When the back pressure chamber pressure becomes excessive, the solenoid valve 23
Open and close a to release the excess back pressure to the low pressure side,
Control the back pressure chamber pressure to maintain it at an appropriate value. By doing so, according to the present embodiment, (1) the back pressure chamber pressure can be optimally changed no matter how the rotational speed and pressure conditions of the scroll fluid machine change; In other words, (a) Even if the suction pressure decreases, which occurs during unsteady conditions such as during start-up or transition to low-speed rotation, for example, excessive backpressure that is more than twice the appropriate backpressure chamber pressure value is generated. (b) When the discharge pressure decreases, even if the back pressure chamber pressure value becomes relatively excessive back pressure, the excess back pressure can be released to the suction passage extremely quickly. As a result, an increase in sliding friction loss and damage between both scrolls can be prevented.

(2) When a scroll fluid machine is started from a state where suction pressure and discharge pressure are balanced, the pressure ratio changes from 1 to gradually increase. Follow the changes that occur once the value becomes small and then increases. The back pressure value can be made to follow such changes, and as a result, it is possible to prevent an increase in sliding friction loss and damage between both scrolls, and it is possible to suppress the starting current to a small value.

Furthermore, in the case of an air compressor that frequently starts and stops, a large current frequently flows through the electric motor (not shown) during startup. Therefore, a light load starting method that suppresses the starting current is required. In this case, a solenoid valve 23a is used as the control means 23, and this solenoid valve 23a is linked to the high pressure switch 21 of the pressure tank 20.
When the air pressure discharged into the pressure tank 20 reaches the high set pressure, the solenoid valve 23a is opened, and the pressure gas in the back pressure chamber 35 is released to the suction system side, which is the suction pipe 18, and the back pressure chamber 35 The pressure in the back pressure chamber is reduced very quickly to a low pressure close to the suction pressure. Due to the above action, the above-mentioned axial pressing force Fs no longer acts, and the compression action by the orbiting scroll 2 and the fixed scroll 1 becomes 100% unloaded. That is, if the axial pressing force Fs does not act,
This is because the orbiting scroll 2 is separated from the fixed scroll 1 in the axial direction, and the sealing of the end surfaces of the laps 1b and 2b becomes incomplete. At this time, pressure introduction pipe 1
No. 6 solenoid valve 15a is already closed. This method can also be applied when restarting a scroll fluid machine after it has stopped operating, and since no axial pressing force is applied due to pressure difference, any startup or
Light load startup is also possible when restarting. Fourth
The figure shows the above control circuit, and between the power supply lines RS,
A push button switch 26b for "off", a push button switch 26a for "on", a thermal relay 28, and an electromagnetic switch 27 for the compressor motor are connected in series, and the electromagnetic switch for the compressor motor is connected in parallel to the pressure switch 26a. The tangential contact 27a of the device is connected. Further, the contact point 21' of the aforementioned high pressure switch and the solenoid valve 23a are connected in parallel to the thermal relay 28 and the electromagnetic switch 27. If you press the electric button switch 26a,
The thermal relay 28 and the electromagnetic switch 27 of the motor are energized, their contacts 27a are closed, and the compressor is operated. The contact 21' of the high pressure switch 21 and the solenoid valve 23a are interlocked, and the pressure switch 21
is opened, the solenoid valve 23a is demagnetized, its passage is opened, and the compressor continues to operate even though it is in an almost no-load state.

As a result, the stop push button switch 2
As long as a does not operate, the compressor is always operated even in a no-load state, and the starting current is not repeatedly applied frequently, so the power supply capacity can be smaller.

As described above, according to this embodiment, (1) Even when the scroll fluid machine is once stopped, the pressure in the back pressure chamber can be brought to the same pressure as the suction pressure very quickly, and any startup or restart is possible. Light load startup is also possible.

(2) The pressure in the back pressure chamber can be brought to the same pressure as the suction pressure very quickly when desired, and since the orbiting scroll is separated from the fixed scroll in the axial direction, 100% unload operation can be performed, and the air compressor When used as a pump, there is no need to stop the scroll fluid machine even when the set discharge pressure is reached, the starting current can be kept low, and the power supply capacity can be smaller.

There are effects such as

Next, when a flow rate control valve is used as the control means 23 as a throttle valve, the amount of gas passing from the back pressure chamber 35 to the suction pipe 18 side (bypass amount) is limited, and the back pressure level is kept at a certain minimum value. Can be adjusted.

Further, as the control means 23, a pressure relief valve may be used that releases the high back pressure to the low pressure suction side when the pressure in the back pressure chamber 35 becomes abnormally high. If this relief valve is used, even if the back pressure rises abnormally due to any of the reasons mentioned above, the high pressure gas in the back pressure chamber 35 will be quickly released to the low pressure side, and the excessive thrust pressing force will be removed from the wrap tip, end plate, etc. There is no need to apply pressure to the sliding parts, improving the reliability of the compressor.

FIG. 5 shows still another embodiment of the present invention. This embodiment has the function of the pressure relief valve described above, and is an example in which a control means is formed within the compressor main body. That is, back pressure relief holes 29a and 29b are provided to directly communicate between the suction port 1c of the fixed scroll 1 and the frame 9 forming the back pressure chamber 35, a valve chamber 35 is formed in the middle, and a steel ball is inserted into this valve chamber. valve body 3
0 and a spring 32 that presses the valve body through the seat plate 31.
has been set up. 34a and 34b indicate O-rings. Other parts are the same as in FIG. 3. When the pressure in the back pressure chamber 35 is lower than the required minimum value, the valve body 30 is released by the pressure of the spring 32 into the back pressure relief hole 29.
A is closed and normal operation is performed. When the suction pressure decreases and the back pressure in the back pressure chamber 35 becomes abnormally high, the pressure overcomes the pressing force of the spring 32 and pushes down the valve body 30, opening the relief hole 29a and transferring the back pressure to the suction port 1c. to escape. By adjusting the elastic force of the spring 32, the back pressure generated in the back pressure chamber 35 can be adjusted. The steel ball valve body 30 may form a wedge shape as a valve structure, and this control means may be controlled by the orbiting scroll end plate 2a facing the suction chamber 40.
The same effect can be obtained even if it is installed in the section. In addition, although the above-mentioned embodiment explained an example of a scroll fluid machine for an air compressor, the present invention is not limited to the above-mentioned embodiment, and may also be applied to a refrigerant compressor for refrigeration and air conditioning. Of course.

〔Effect of the invention〕

As explained above, according to the present invention, even if the rotational speed and pressure conditions of the scroll fluid machine change, the suction pressure decreases, and the back pressure chamber pressure becomes excessive, the pressure of the fluid supply section and the on-off valve The excess amount can be quickly eliminated without controlling the amount. For example, even if suction pressure drops during unsteady conditions such as during start-up or transition to low-speed rotation, resulting in excess backpressure that is more than twice the appropriate backpressure chamber pressure value, the excess backpressure can be removed very quickly. It can escape into the suction tract. As a result, an increase in sliding friction loss and damage between both scrolls can be prevented.

According to the embodiment in which the valve device is an on-off valve such as a solenoid valve, in addition to this, (1) When the scroll fluid machine is started from a state where the suction pressure and the discharge pressure are balanced, the pressure ratio gradually increases from 1. Immediately after startup, the appropriate value of the back pressure changes as it becomes smaller than the balance pressure and then becomes larger. The back pressure value can be made to follow such changes, and as a result, it is possible to prevent an increase in sliding friction loss and damage between both scrolls, and it is possible to suppress the starting current to a small value.

(2) Even when the scroll fluid machine is stopped, the pressure in the back pressure chamber can be brought to the same pressure as the suction pressure very quickly, and light load startup is possible for any startup or restart.

(3) The pressure in the back pressure chamber can be brought to the same pressure as the suction pressure very quickly when desired, and since the orbiting scroll is separated from the fixed scroll in the axial direction, 100% unload operation can be performed, and the air compressor When used as a pump, there is no need to stop the scroll fluid machine even at a set discharge pressure, and the starting current can be kept low, so the power supply capacity can be smaller. Therefore, it is necessary to apply a starting method and unloader method to scroll fluid machines that can prevent abnormal back pressure rise in the back pressure chamber that greatly affects performance, prevent damage to the compressor, and suppress starting current. It has effects such as being able to.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a conventional scroll fluid machine, FIG. 2 is a cross-sectional view showing a scroll meshing state, FIG. 3 is a vertical cross-sectional view of a scroll fluid machine showing an embodiment of the present invention, and FIG. The figure is a control circuit diagram, 5th
The figure is a fragmentary enlarged sectional view showing another embodiment. DESCRIPTION OF SYMBOLS 1... Fixed scroll, 1a... Flat plate part, 1b... Wrap part, 1c... Suction part, 1d... Discharge port, 2... Orbiting scroll, 2a... End plate, 2b... Wrap part, 3...
Oldham key, 4... Oldham ring, 9... Outer frame, 14... Suction filter, 15... Pressure source, 15
a...Solenoid valve, 16...Pressure introduction pipe, 18...Suction pipe,
19...Discharge pipe, 20...Pressure tank, 21...High pressure switch, 21'...Contact, 23...Control means, 2
3a... Solenoid valve, 24... Bypass path, 29a, 2
9b...back pressure relief hole, 30...valve body, 32...spring, 3
5...Back pressure chamber.

Claims (1)

[Scope of Claims] 1. An orbiting scroll and a fixed scroll are engaged with each other, a back pressure chamber is formed at the back of the orbiting scroll, and a back pressure chamber pressure is generated by fluid supplied to the back pressure chamber from a fluid supply section. In the scroll fluid machine that presses the orbiting scroll against the fixed scroll, the back pressure chamber and the suction passage are connected through a valve device that releases excess pressure of the back pressure chamber to the suction passage during unsteady operation. A scroll fluid machine characterized by communicating with each other. 2. The scroll fluid machine according to claim 1, wherein the valve device is a solenoid valve, and the back pressure chamber pressure is controlled by opening and closing the solenoid valve. 3. The scroll fluid machine according to claim 1, wherein the valve device is a flow control valve. 4. The scroll fluid machine according to claim 1, wherein the valve device is a pressure relief valve. 5. The scroll fluid machine according to claim 1, wherein the valve device comprises a valve body and a pressing spring, and the pressing force of the pressing spring is set to correspond to a necessary minimum value of the pressure level of the back pressure chamber. 6. The valve device is a solenoid valve, and when the set pressure is exceeded due to cooperation with a pressure switch, the fluid supply section is closed, the solenoid valve is opened, and the back pressure chamber pressure is controlled to the suction pressure state. Scroll fluid machine according to claim 1, characterized in that: