JP2581352B2 - Compressor protector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protective device such as a screw compressor or a scroll compressor, and more particularly, to a compressor formed with a compression chamber between two relatively rotating members. Decreases with increasing temperature,
The present invention relates to a protection device for preventing these two members from contacting each other and causing a failure.

[0002]

2. Description of the Related Art Conventionally, as a protection device for a compressor of this type, for example, a screw compressor, it is described in Japanese Utility Model Laid-Open Publication No. 63-190585, and a screw rotor B is provided in a casing A as shown in FIG. The casing A is rotatably provided to form a compression chamber C between the casing A and the screw rotor B. The temperature of the casing A is set on the inner wall of the casing A near a discharge gas passage D extending from the compression chamber C. A first temperature detector E for detecting the temperature is disposed, and a second temperature detector F for detecting the temperature of the discharge gas is disposed near the compression chamber C in the discharge gas passage D, while the first and second temperature detectors E are provided. (2) The temperature detectors E and F are connected to a controller with a built-in CPU, and the first temperature detector E detects the temperature of the casing A whose temperature change is relatively gradual. When the difference between the discharge gas temperatures detected by the discharger F is a temperature difference at which the clearance provided between the casing A and the screw rotor B exceeds an allowable limit, liquid injection into the compressor is performed by the output from the controller. Or the motor of the compressor is stopped.

[0003]

However, in the above protective device, the first temperature detector E for detecting the temperature of the casing A and the second temperature detector for detecting the temperature of the discharge gas passing through the discharge gas passage D. A temperature difference is calculated using the detector F and based on the detection results of the detectors E and F. When the temperature difference exceeds the allowable limit of the clearance, the compressor outputs the fluid to the compressor by the output of the controller. Since the injection is performed or the motor of the compressor is stopped, there is a problem that the structure becomes complicated and the cost increases.

As a protection device for the compressor, conventionally, a temperature switch is interposed in the discharge gas passage D,
When the temperature of the discharge gas passing through the discharge gas passage D becomes equal to or higher than a certain value, there is also known a device in which the compressor is stopped by the temperature switch, but such a protection device has a simple structure. On the other hand, the casing A and the screw rotor B may come into contact with each other before the temperature switch is activated when the temperature of the discharged gas suddenly rises in the low operating state.

[0005] That is, in general, in a refrigerator, the operating condition changes rapidly between when the condenser is operated at a low temperature (for example, 30 ° C) and when the condensing temperature is high (for example, 50 ° C). When the discharge gas temperature rises due to lack of refrigerant gas or the like, the rise gradient of the discharge gas temperature is different. Therefore, if the set temperature of the temperature switch is set to a predetermined temperature (for example, 100 ° C.), under low operating conditions, During operation, the time required for the discharge gas temperature to reach the set temperature is longer than when operating under high operating conditions. Is reduced at a constant rate with the elapse of time as the temperature of the discharged gas rises, so that low operating conditions (condensation temperature of 30 ° C.)
When the superheat degree is 25 ° C., the discharge gas temperature during the steady operation becomes 55 ° C.
From 5 ° C. to the set temperature of 100 ° C., the clearance decreases and the casing A and the screw rotor B come into contact.

In this case, it is conceivable to lower the set temperature of the temperature switch. However, if the temperature is set low, the operation of the compressor is stopped even if there is a sufficient clearance under the operating condition where the condensing temperature is high. Therefore, there is a problem that the operating range is narrowed accordingly.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a protection device having a simple structure and capable of preventing a failure due to contact between two members over a wide operating range. To provide.

[0008]

In order to achieve the above object, according to the present invention, in a compressor in which a compression chamber 3 is formed between two relatively rotating members 1 and 2, a temperature rise between the two members 1 and 2 is caused. A temperature sensor 7 having a two-step temperature switch 71 that operates at a set temperature different from the detected temperature, and detects a discharge gas pressure. A pressure sensor 8 having a pressure switch 81 that operates at a set pressure. When the pressure switch 81 is not operated, the low-temperature contact of the temperature switch 71 is operated, and when the pressure switch 81 is operated, the temperature switch 71 is operated. A protection circuit 9 for stopping the driving of the compressor by operation of the high-temperature contact is provided.

[0009]

During the operation of the compressor, the pressure of the discharge gas discharged from the compression chamber 3 is increased to a predetermined set pressure, for example, the condensation temperature 4.
Equivalent saturation pressure of 0 ° C (about 15K for Freon R-22)
g / cm ² ) or less, the pressure switch 81 is kept in a non-operating state, and when the temperature of the discharge gas rises in this state, the low-temperature contact included in the two-step temperature switch 71 operates, The compressor is stopped by the output from the protection circuit 9 accompanying the operation of the low-temperature contact. When the pressure of the discharge gas discharged from the compression chamber 3 exceeds the predetermined set pressure, the pressure switch 81
Is maintained in the operating state, and when the temperature of the discharge gas rises in this state, the high-temperature contact provided in the two-step temperature switch 71 operates, and the output from the protection circuit 9 accompanying the operation of the high-temperature contact is The compressor is stopped. As described above, the gas pressure discharged from the compression chamber 3 is detected by the pressure switch 81, and the protection circuit 9 is activated by operating the low-temperature or high-temperature contact provided in the two-step temperature switch 71 based on the detection result. The protection control of the compressor is accurately performed irrespective of the operating conditions by stopping the compressor by outputting from the
The contact of the members can be prevented. Moreover, by stopping the compressor using the two-step temperature switch 71 that operates based on the operation and non-operation of the pressure switch 81, the compressor can be protected over a wide operating range.

[0010]

1 and 2 show a screw compressor as an example of a compressor in which a compression chamber 3 is formed between two members 1 and 2 which rotate relative to each other. A screw rotor 2 serving as the other side member is opposed to a screw rotor 2 serving as a member on the outer peripheral surface of the screw rotor 2 with a predetermined clearance between the screw groove 2 a and an inner wall 1 a of the casing 1. And a compression chamber 3 is formed between the inner wall 1a and the screw groove 2a. Also,
At the side of the screw rotor 2, its screw groove 2
a, a pair of gate rotors 4 having meshing teeth meshing with each other are provided, and a motor 5 is provided on the inner side of the casing 1, and the screw rotor 2 is connected to the gate by a drive shaft 51 extending from the motor 5. While the rotor 4 is driven to rotate, a slide valve 6 slidable in the axial direction is arranged near the refrigerant gas discharge side of the screw rotor 2.

Then, by rotating the screw rotor 2 and the gate rotor 4 with the driving of the motor 5, the suction chamber 1 formed in the casing 1 is rotated.
After sucking a low-pressure refrigerant gas into the compression chamber 3 and compressing the compressed gas in the compression chamber 3, the oil is recovered from the discharge port 12 formed in the slide valve 6 through the discharge chamber 13 provided in the casing 1 to the oil recovery device 14. Is discharged. Further, on the inner wall 1a of the casing 1, there is provided an elongated opening 16 which partially opens into the suction chamber 11 to form a bypass port 15, and communicates with the discharge chamber 13 in the middle of the opening 16, The slide valve 6 is slidably disposed in the opening 16, and the position of the discharge port 12 is changed by sliding operation of the slide valve 6, and the opening of the bypass port 15 is changed. Thus, a capacity control operation of the compressor can be performed.

In the screw compressor as described above, the clearance formed between the casing 1 and the screw rotor 2 decreases due to a rise in temperature.
A protection device for preventing the casing 1 and the screw rotor 2 from contacting each other and causing a failure is provided.
The configuration is as follows.

That is, as shown in FIGS. 1 and 2, a two-step temperature switch 71 which detects the temperature of the discharge gas discharged from the compression chamber 3 and operates at a different set temperature with respect to the detected temperature is provided. Temperature sensor 7 and the compression chamber 3
And a pressure sensor 8 having a pressure switch 81 that operates when the detected pressure is a predetermined set pressure. The temperature sensor 7 is connected to a discharge port 12 in the casing 1. The pressure sensor 8 is disposed so as to protrude into the discharge chamber 13, and switches 71 and 81 are provided on the output side of the temperature sensor 7 and the pressure sensor 8.
And a protection circuit 9 for stopping the motor 5 is connected through
When the pressure switch 81 is not operated, the output from the protection circuit 9 is performed based on the operation of the low-temperature contact provided in the two-step temperature switch 71 to stop the motor 5, and
When the pressure switch 81 is operated, the motor 5 is stopped by outputting from the protection circuit 9 based on the operation of the high-temperature contact provided in the two-step temperature switch 71.

Next, a control mode of the protection device having the above configuration will be described. First, FIG. 3 shows an operation state of the temperature switch 71 and the pressure switch 81 with respect to a set pressure. For example, the temperature at which the set pressure is set to 15 kg / cm ² and the low-temperature contact of the temperature switch 71 operates. At 90 ° C and the temperature at which the high-temperature contact operates at 100 ° C
When the pressure detected by the pressure switch 81 is lower than the set pressure, the pressure switch 8
1 is turned off, the low-temperature contact of the temperature switch 71 is turned on / off with reference to 90 ° C., and when the pressure detected by the pressure switch 81 is higher than the set pressure, the pressure switch 81 Is turned on, and the high-temperature contact of the temperature switch 71 is turned on / off with reference to 100 ° C.

FIG. 4 is a graph in which the vertical axis represents the temperature and clearance of the discharge gas, and the horizontal axis represents the operation time.
In the figure, the curve shown by the solid line indicates that the discharge gas temperature is 75 ° C.
The curve indicated by the dashed line indicates the temperature change with respect to the operation time when the discharge gas temperature is 55 ° C., and the curve indicated by the dotted line indicates the temperature change with respect to the operation time when the casing 1 and the screw rotor 2 change with respect to the operation time. , Respectively, indicates the change in clearance between the two. Note that the curve shown by the solid line shows the discharge gas temperature at a degree of superheating of 25 ° C., the condensation temperature of which is 50 ° C., and R22 as the refrigerant.
The saturation pressure corresponding to the condensing temperature of 50 ° C. when using is about 18.8 kg / cm ² , and the curve shown by the dashed line indicates the discharge gas temperature at which the superheat degree is 25 ° C. The condensing temperature is 30 ° C., and the saturation pressure corresponding to the condensing temperature of 30 ° C. when R22 is used as the refrigerant is about 11.2 kg / cm ² ,
When the operating conditions are different as described above, the rising gradient in the case where the operating conditions change suddenly or the refrigerant gas runs out of gas and the discharge gas temperature rises is different.

Therefore, when the temperature at which the operation of the compressor is stopped is set to, for example, 100 ° C. as in the prior art, the time required for the discharged gas to reach the set temperature under the operating conditions with a low condensing temperature depends on the high condensing temperature. Under operating conditions, the time is longer than the time required to reach the set temperature, and in the middle, the clearance exceeds the allowable limit and comes into contact.

Therefore, the temperature switch 71 is set in two steps to change the operating temperature for stopping the compressor on the basis of the pressure of the discharge gas. The temperature is a saturation pressure equivalent to 40 ° C. (about 15 kg / cm ^{2 for} R-22).

During the operation of the compressor, the pressure of the discharge gas discharged from the compression chamber 3 becomes equal to the set pressure (1).
If it is higher than 5 kg / cm ² ), for example, the discharge gas temperature 7
When operating at 5 ° C., as is apparent from FIG. 3, when the pressure switch 81 is kept on and the temperature of the discharge gas rises from 90 ° C. to 100 ° C.,
The high-temperature contact provided on the step temperature switch 71 operates,
As shown in FIG. 4, at the point B instead of the point A, a stop signal is output from the protection circuit 9 to the motor 5, and the motor 5 is stopped within the allowable limit clearance range of the clearance curve. On the other hand, when the pressure of the discharge gas discharged from the compression chamber 3 is lower than the set pressure, for example, when operating at a discharge gas temperature of 55 ° C., as is apparent from FIG. When the temperature of the discharge gas is kept at the off state and the temperature of the discharge gas rises to 90 ° C., the low-temperature contact provided in the two-step temperature switch 71 is activated, and as shown in FIG. A stop signal is output from the protection circuit 9 to the motor 5 side, and the motor 5
Is stopped within the allowable limit clearance range of the clearance curve.

As described above, the pressure of the gas discharged from the compression chamber 3 is detected by the pressure switch 81, and the operation of the low-temperature or high-temperature contact provided in the two-step temperature switch 71 based on the detection result causes the above-mentioned operation. By outputting from the protection circuit 9 and stopping the motor 5, the protection control of the compressor is performed more easily and more reliably than in the conventional example, and the operation of the pressure switch 81 By stopping the motor 5 using a two-step temperature switch 81 having high and low temperature contacts that operate based on non-operation, the protection device operates to stop the compressor despite sufficient clearance. In other words, as described in the conventional example, when the set temperature of the temperature switch is reduced, the discharge gas temperature may increase under the operating condition where the condensing temperature is high. Although the temperature switch operates to stop the compressor despite sufficient clearance, the set temperature at which the operation is performed can be changed according to the operating conditions, so that the above-described problem of the conventional example does not occur. Therefore, the operating range can be extended correspondingly, and the compressor can be protected over a wide operating range.

In the above embodiment, the case where the present invention is applied to a screw compressor has been described. However, the protection device of the present invention can be applied to a scroll compressor and the like.

[0021]

As described above, according to the protection device of the present invention, the temperature sensor 7 having the two-step temperature switch 71 which detects the discharge gas temperature and operates at a different temperature from the detected temperature, A pressure sensor 8 having a pressure switch 81 that detects a gas pressure and operates at a set pressure. When the pressure switch 81 is not operated, the low-temperature contact of the temperature switch 71 operates to operate the pressure switch 81. Since the protection circuit 9 for stopping the operation of the compressor by the operation of the high-temperature contact is sometimes provided, the clearance formed between the two relatively rotating members 1 and 2 is increased by a simple configuration regardless of the operating conditions. Accordingly, it is possible to reliably prevent the members 1 and 2 from coming into contact with each other and failing. Work, since it is possible to change the operating temperature of stopping the compressor by non-operating, it is possible to perform protection control of the compressor over a wide operating range.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a main part of a screw compressor provided with a protection device of the present invention.

FIG. 2 is a front sectional view showing a main part of the screw compressor.

FIG. 3 is an explanatory diagram illustrating operating states of a temperature switch and a pressure switch.

FIG. 4 is a graph showing a change in discharge gas temperature and a change in clearance with respect to an operation time.

FIG. 5 is a front sectional view showing a compressor protection device according to a conventional example.

[Explanation of symbols]

 1, 2 member 3 compression chamber 7 temperature sensor 71 2 step temperature switch 8 pressure sensor 81 pressure switch 9 protection circuit

Claims (1)

(57) [Claims] A compression chamber (3) between two relatively rotating members (1, 2).
A protective device for protecting against a decrease in clearance due to a rise in temperature between the two members 1 and 2 in the compressor that forms the two-step temperature, wherein the set temperature at which the discharge gas temperature is detected and which operates with respect to the detected temperature is different. A temperature sensor 7 having a switch 71; and a pressure sensor 8 having a pressure switch 81 which detects a discharge gas pressure and operates at a set pressure. When the pressure switch 81 is not operated, the temperature of the temperature switch 71 is low. A protection device for a compressor, comprising: a protection circuit 9 for stopping operation of the compressor by operation of a high-temperature contact when the pressure switch 81 operates when a contact operates.