JPS6258079A - Capacity control mechanism for screw compressor - Google Patents

Abstract

PURPOSE:To prevent burning of a drive motor under full-close of a capacity control valve by providing a mechanism for stopping the drive motor after operating for a predetermined time interval at the lock position exceeding over the full-close set position of the capacity control valve in the close drive control circuit of the drive motor for the capacity control valve. CONSTITUTION:Under closing operation of a capacity control valve 10, operation of a drive motor 20 for the capacity control valve 10 will continue until the capacity control valve 10 will pass over the full-close set position and reach to the lock position. The operation of the drive motor 20 is controlled through stop a mechanism such that it will be stopped upon elapse of a predetermined time interval after reaching of the capacity control valve 10 to the lock position. Consequently, even if there is a clearance such as a backlash in the drive transmission mechanism of the capacity control valve 10, the capacity control valve 10 can be closed reliably while burning of the drive motor 20 due to continuous operation at the lock position can be prevented.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention provides a capacity control mechanism for a screw compressor, specifically, an intermediate opening is provided between a suction chamber and a discharge chamber, and an opening of the intermediate opening is provided between a suction chamber and a discharge chamber. The present invention relates to a capacity control mechanism that controls the capacity of a compressor by adjusting the area with a capacity control valve.

(Prior art) In conventional screw compressors, an intermediate opening is provided,
It is generally known that the capacity is controlled by adjusting the opening area of the intermediate opening with a capacity control valve.

Incidentally, the capacity control valve is normally a slide valve that is reciprocated with respect to the intermediate opening, and is also connected to a motor via an interlocking mechanism using gears, so that it is mechanically driven by the motor. However, when the capacity control valve is mechanically operated by such a motor drive, there is a bank lash when the motor is driven, and this backlash prevents the capacity control valve from being correctly operated to the fully closed set position. In other words, it is normal that the valve opening cannot be made 0% at this fully closed set position.

Furthermore, when controlling the number of customers by adjusting the opening area of the intermediate opening using the capacity control valve, the ability of the capacity control valve to adjust the opening of the intermediate opening is not proportional as shown in FIG. As the position approaches, the reduction ratio of the capacity to the degree of opening in the opening direction increases.

Therefore, unless the valve is fully closed at the fully closed set position as described above, the performance will be significantly reduced and the desired performance will not be obtained.

In order to solve the above-mentioned problems, a capacity control mechanism has been proposed in which the capacity control valve is driven by a motor, in which the discharge pressure of the refrigerant is used to ensure full closure.

This capacity control mechanism is shown in Japanese Patent Application Laid-Open No. 59-229077, and as shown in FIG. An intermediate boat (P,) is provided between the intermediate boat (P,), and a slide valve (V) that changes the opening area of the intermediate boat (P,) is freely supported. The operating rod (A) of the slide valve (V) is interlocked with a motor (M) through a drive mechanism (D) consisting of a plurality of gears, and is fully controlled by the drive of the motor (M). ), a balancer (B) sandwiching the discharge boat (P, ) and facing the slide valve (V).
A balancer (B) facing the discharge boat (P
) and the slide valve (V), and the slide valve (V) is allowed to move within a certain range with respect to the stop position set by the limit switch of the motor (M), and the discharge board ) (PI) is used to urge the slide valve (V) in the closing direction so that the intermediate bow (P3) can be fully closed.

In FIG. 3, (E) is an unbalanced piston for forming an area difference between the opposing surfaces of the balancer (B) and slide valve (V), and (F) is 1) τ1 intermediate port (
P3) is a bypass passage that communicates with the suction boat (Pl) side, and (H) is a bypass passage that communicates with the rear chamber (P3) of the balancer (B).
J) is a communication path that communicates with the bypass path (F).

In this conventional example, when the slide valve (V) is fully closed, the motor (M) closes the slide valve (V).
This is done by driving the slide valve (V) to a fully closed set position set by a limit switch, and in this fully closed set position, the slide valve (V) is
) is applied in the opening direction by multiplying the discharge pressure by the area difference between It is completely closed.

(Problem to be Solved by the Invention) However, according to this conventional example, the opening degree of the slide valve (V') can be guaranteed to be 0% at the fully closed set position; ) to the operating rod (A) of the balancer (B).
), and this balancer (B)
The opposing surface facing the discharge port (P,) and the slide valve (V)
It is necessary to provide a means for forming an area difference between the opposing surface facing the discharge bow (Pg), which complicates the structure, and when controlling from the fully closed position to the open direction, the slide valve (V) It is necessary to operate the slide valve (V) against the biasing force due to the difference in area acting on the motor (M), which causes the problem of increasing the load on the motor (M).

An object of the present invention is to have a simple configuration and to be able to guarantee full closure of a capacity control valve without burning out the motor.

(Means for Solving the Problems)) The present invention provides a casing (1) provided with an intermediate opening (8) that communicates with a suction chamber (5).
A control motor (20) that freely supports a capacity control valve (10) that changes the opening area of the opening (8) and drives the capacity control valve (10) reciprocatingly in the opening and closing directions with respect to the opening (8). A capacity control mechanism for a screw compressor, which is provided with a drive signal for the control motor (20) to drive the motor (20), and a capacity control valve (10) for driving the motor (20).
) is provided with a controller (40) that outputs a fully closed drive signal based on the fully closed signal of the controller (40).
), the closing drive control circuit of the motor (20) is provided with a stop mechanism that stops the drive of the motor (20) at a lock position when the capacity control valve (10) exceeds the fully closed set position. This is a characteristic feature.

(Function) A fully closed input signal of the capacity control valve (10) causes the motor (2
0) to fully close the capacity control valve (10), drive and control the motor (20) so that the capacity control valve (10) moves beyond the fully closed set position and toward the lock position. With this drive, backlash can be absorbed and the intermediate opening (8) can be reliably controlled to be fully closed. The drive of the motor (20) is stopped by the stop mechanism, and this stop does not cause burnout of the motor.

(Example) The one shown in Fig. 2 is a single screw compressor used in a refrigeration system, in which one screw rotor is installed in the compression chamber (2) of a casing (1) equipped with a compression chamber (2). (3) and this screw rotor (3)
A pair of gate rotors (4) are engaged with each other, and by the rotation of these rotors (3) and (4), low pressure gas refrigerant is sucked from the suction chamber (5) and compressed in the compression chamber (2).
It is designed to be discharged from a discharge port (6).

The casing (1) also has an intermediate opening (1) located between the suction chamber (5) and the discharge port (6) and communicating with the suction chamber (5) via a bypass path (7). 8), and this intermediate opening (8)
The opening area of the valve is changed by the capacity control valve (10) to control the capacity.

The capacity control valve (10) has a circular inner surface with the same arc as the inner circumferential surface of the casing (1), and is composed of a valve body with a three-month cross section.
) The interior can be moved freely.

Further, this capacity control valve (10) is connected to a control motor (20).
The control valve (10
) is provided with an operating rod (12) that extends outside through the casing (1), and the operating rod (12) extends outwardly through the casing (1).
The outer end of 2) is a rack (12a), which is linked to the motor (20) via a gear transmission mechanism (30).

This gear transmission mechanism (30) includes a drive shaft (32) having a drive gear (31) that meshes with a transmission gear (22) fixed to the motor shaft' (21) of the motor (20);
A driven wheel (34) and a pinion gear (35) (36) interlock with this drive shaft (32) via a transmission gear (33).
), and the pinion gear (35) (
36) is meshed with each rack (12a) of the capacity control valves (10) (10) formed integrally with the casing (1), and the driving force of the motor (20) is transferred to the pinion (35). (3B) and these pinions (35) (
The respective capacity control valves (10) (10) are driven through the rack (12a) that meshes with the valve (12a).

The control motor (20) uses the sequence controller (40) shown in FIG. The valve opening degree of the capacity control valve (10) is controlled to a predetermined valve opening degree by, for example, PID control using the signal and the feedback signal from the motor (20).

The load detection means (41) is connected to the input side of the controller (40) shown in FIG. 1, and a rotation angle detection means (42) is connected to the input side of the controller (40) and outputs a feedback signal in conjunction with the rotation of the motor (20). It connects the
Further, on the output side, there is a switch (SW) whose contacts are closed when the brine temperature input from the load detection means (41) is lower than the set temperature, and a relay for opening drive control (SW).
43), and a switch (SW) that closes when the brine temperature is higher than the set temperature.
, ), a cycle timer relay for closing drive control (45) connected in series to this switch (SW, ), and a timer relay (46) for controlling stop during closing drive. ).

Of the circuits (49) and (50) connected to the power source that connect the motor (2Q) to the power source via the transformer (48), the circuit that drives the capacity control valve (10) in the opening direction (
The opening drive control relay (49) is connected to the reversing circuit (49).
3), the normally open contact (43-,) is interposed, and the circuit (normal rotation circuit) (50) for driving the capacity control valve (10) in the closing direction is provided with the normally open contact (43-,) for controlling the closing drive. The contact (45-1) of the cycle timer relay (45) and the contact (46-I) of the timer relay (46) are interposed. The contact (45-1) is turned ON for 1 second and then turned OFF for 5 seconds, and the cycle timer relay (45) is used to continuously operate when the capacity control valve (10) is closed. This is to prevent liquid refrigerant from being sucked in if the suction amount is suddenly increased by closing the valve.

Further, the switch (SW) of the closing drive control circuit (47)
, ) operates based on a signal from the load detection means (41) with a fully closed signal that fully closes the capacity control valve (10), when the capacity control valve (10) is set to fully closed. In other words, the motor (20) moves to a locking position beyond a fully open position preset by the rotation angle of the motor (20), that is, a position in which the motor (20) absorbs backlash and does not rotate any further. The ON operation continues until the

In other words, the controller (40) controls the motor (2).
0) to drive the motor (20) in the forward or reverse direction, and when driving it based on the fully closed signal, the motor (20) is driven beyond the fully closed set position to the lock position side. It is structured as follows.

Further, a timer relay (46) provided in the closing drive control circuit (47) stops the drive of the motor (20) at the lock position by time control when the capacity control valve (10) exceeds the fully closed set position. It constitutes a stopping mechanism that
The time setting of the timer relay (46) is slightly longer than the time required for the motor (20) to fully open the capacity control valve (10), for example, the time required for fully closing the valve is 5 degrees.
minute, it is set to 6 minutes, and the controller (
If the closing direction drive signal from 40) continues for 6 consecutive minutes, that is, if the on-operation time of the switch (SW, ) of the closing drive control circuit (47) exceeds 6 minutes, the power supply of the motor (20) is turned on. The circuit (50) is cut off.

In addition, in Fig. 1, (51) is the opening direction drive circuit (49).
A limit switch installed in the capacity control valve (10
) to stop the drive of the monitor (20) which performs the opening operation.

Therefore, in the embodiment described above, the fully closing control of the capacity control valve (10) is performed by driving the motor (20) beyond the fully closed set position toward the lock position. Therefore, the λ wheel transmission mechanism (3
Even if there is a pack rush at 0), the capacity control valve (10) can be reliably fully closed with a simple structure.

Moreover, the drive of the motor (20) beyond the fully closed set position of the capacity control valve (10) is reliably stopped by the timer relay (46) that constitutes a stop mechanism.
Burnout due to overload of the motor (20) can also be reliably prevented.

In the embodiment described above, the timer relay (46) is used to stop the drive of the motor (20) beyond the fully closed set position.
), and this is done by time control, but in addition, the lock position is detected by stopping the rotation of the motor (20),
It may be performed based on this detection result.

Further, although a single screw compressor has been described as an example, the present invention can also be applied to a double screw compressor, a tandem compressor, or a two-stage compressor. Further, the present invention is not limited to compressors of refrigeration equipment, and can be similarly applied even when air is used as the working fluid.

(Effects of the Invention) As described above, the present invention allows the drive of the control motor (20) that drives the capacity control valve (10) in the closing direction to be controlled by the capacity control valve (10).
Since the drive is made to exceed the fully closed set position of 10), even if there is backlash in the transmission mechanism, the capacity control valve (10) can be reliably fully closed with a simple structure. They are made to do so.

Therefore, it is possible to carry out full operation according to the set capacity, and the problem of insufficient capacity can be solved.

Furthermore, since the drive of the motor (20) beyond the fully closed set position is stopped at the lock position by the stop mechanism, there is no problem of motor burnout due to overload.

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram showing an embodiment of the present invention, FIG. 2 is a schematic cross-sectional explanatory diagram showing an example applied to a single screw compressor, and FIG. 3 is a schematic explanatory diagram showing a conventional example. FIG. 4 is a drawing showing the relationship between the opening degree and capacity of the capacity control valve. (1)...Casing (5)...Suction chamber (8)...Middle opening

Claims (1)

[Claims] (1) Intermediate opening (8) communicating with suction chamber (5)
) with said intermediate opening (8)
A control motor (2) freely supports a capacity control valve (10) that changes the opening area of the opening, and drives the capacity control valve (10) reciprocatingly in the opening and closing directions with respect to the opening (8).
0), which provides a drive signal to the control motor (20) to drive the motor (20), and provides a fully closed signal for the capacity control valve (10). A controller (40) is provided which outputs a fully closed drive signal based on the above, and a fully closed set position of the capacity control valve (10) is set in the close drive control circuit of the motor (20) in this controller (40). A capacity control device for a screw compressor, characterized in that a stop mechanism is provided to stop the drive of the motor (20) at a lock position.