JP4895752B2 - Screw compressor and control method of screw compressor - Google Patents

Description

  The present invention relates to a screw compressor technology.

  As this type of screw compressor, for example, there is a technique described in JP-A-6-200886. A conventional screw compressor includes a compressor main body that compresses air, a motor that drives the compressor main body, and an inverter that controls the rotation speed of the motor, and further, discharge air discharged from the compressor main body. Discharge air pressure detection means for detecting pressure and information transmission means for returning the pressure detection value to the motor, and controlling the number of rotations of the motor based on the pressure detection value to adjust the discharge air amount of the compressor It had a function to do.

  However, in the conventional screw compressor described above, the maximum rotational speed of the compressor is fixed even if the set pressure value of the discharge air pressure detecting means is changed, so that the amount of air used on the output side of the compressor is the rated air amount. When the pressure exceeds the range, there has been a situation in which the discharge pressure of the compressor is lower than the required set pressure.

  For example, the maximum rotational speed of the compressor is the same value when the set pressure value for the discharge pressure of the compressor is 0.83 MPa and 0.59 MPa. For this reason, when the set pressure value of the discharge pressure is lowered, the compressor power is reduced and a margin is generated in the motor load (the compressor power is increased when the set pressure value is 0.83 MPa and 0.59 MPa. On the other hand, the maximum discharge air amount of the compressor is almost the same.

  As a result, in the conventional screw compressor, when the amount of air used exceeds a predetermined amount of air, the discharge pressure of the compressor is set to the set pressure even though there is room in the capacity of the motor that drives the compressor. There is a problem that the capacity of the compressor cannot be maximized due to a decrease in the following.

  Therefore, an object of the present invention is to maximize the capacity of the compressor.

A screw compressor according to the present invention is a screw compressor that includes a compressor body and a motor that drives the compressor body, and the number of revolutions of the compressor body is controlled according to the amount of air used by a demand device. , Equipped with discharge pressure setting means that can be set by arbitrarily changing the discharge pressure of the compressor body to a desired discharge pressure, and the discharge pressure set value set by this discharge pressure setting means is set to a pressure lower than the rated pressure In such a case, the maximum rotation speed of the motor is determined so that an air volume larger than the rated air volume is obtained, and the motor is set so that the pressure set by the discharge pressure setting means is within the range of the maximum rotation speed. The number of rotations is controlled. Here, when the discharge pressure set value is set to a pressure lower than the rated pressure, the maximum number of revolutions of the motor is determined so that an air amount larger than the rated air amount can be obtained within the range of the load capacity of the motor. May be. In addition, when the discharge pressure set value is set to a pressure lower than the rated pressure, even if the maximum number of revolutions of the motor is determined with respect to the set pressure value so that an air amount larger than the rated air amount can be obtained. Good.

A screw compressor having a compressor main body for compressing air, a motor for driving the compressor main body, and discharge air pressure detecting means for detecting the pressure of discharge air discharged from the compressor main body. It is configured so that the pressure of the discharge air discharged from the main unit can be changed arbitrarily, and when the set pressure value is lower than the rated pressure, the rated air volume is within the load capacity range of the motor. The maximum rotational speed of the motor is set in advance so as to obtain the above air amount, and the rotational speed of the motor is controlled according to the amount of air used within the range of the set pressure value and the maximum rotational speed. it can.

Furthermore, a compressor main body that compresses air, a motor that drives the compressor main body, an inverter that controls the rotation speed of the motor, a pressure sensor that detects the pressure of discharge air discharged from the compressor main body, In the basic structure of the screw compressor having a rotation speed control means for controlling the operation of the inverter based on the pressure detection value of the pressure sensor to adjust the discharge air amount of the compressor body, the screw is discharged from the compressor body. Equipped with discharge pressure setting means that can be set by changing the pressure of the discharge air arbitrarily. If the pressure set by the discharge pressure setting means is lower than the rated pressure, it will exceed the rated air volume within the compression function force range. The number of rotations of the motor can be controlled according to the amount of air used so that the amount of air can be obtained. Further, in the basic configuration of the screw compressor, when the discharge pressure setting means and the pressure set by the discharge pressure setting means are lower than the rated pressure, the rated air amount is exceeded within the load capacity range of the motor. Motor speed control means for determining the maximum motor speed so that a sufficient amount of air can be obtained, and the motor speed so that the pressure set by the discharge pressure setting means is within the range of the maximum speed. Can be controlled according to the amount of air used. Furthermore, in the basic configuration of the screw compressor, when the discharge pressure setting means and the pressure set by the discharge pressure setting means are lower than the rated pressure, the air pressure exceeds the rated air amount within the compression function force range. The maximum rotation speed control means that can control the rotation speed of the motor so that the amount of air can be obtained, and the rotation speed of the motor is used within the range of the compression function force at the pressure set by the discharge pressure setting means It can also be set as the structure controlled according to air quantity.

Further, a compressor main body that compresses air, a motor that drives the compressor main body, an inverter that controls the rotation speed of the motor, and a pressure sensor that detects the pressure of the discharge air discharged from the compressor main body. In the basic configuration of the provided screw compressor, the pressure of the discharge air discharged from the compressor body can be set to a pressure lower than the rated pressure, and when the pressure is set lower than the rated pressure, the rated air The maximum number of revolutions of the compressor body is changed so that the amount of air exceeding the amount can be obtained and controlled to the set pressure, and the number of revolutions of the motor is controlled according to the amount of air used by the equipment within the maximum number of revolutions. It can be set as the structure to do. Also, in the basic configuration of the screw compressor, when the pressure of the discharge air discharged from the compressor body is set to a pressure lower than the rated pressure, the amount of air that exceeds the rated air amount may also vary depending on the amount of air used. It can be configured to control the number of rotations of the compressor body so that it can be obtained, or the maximum number of rotations of the compressor body is determined so that an air amount larger than the rated air amount can be obtained, and the pressure from the pressure sensor It can also be set as the structure by which the rotation speed of a motor is controlled within the range of the predetermined maximum rotation speed so that it may become a setting pressure based on a detected value. The rated pressure may be a representative pressure value in the product specification, and the rated air amount may be a representative air amount in the product specification.

  According to the present invention, the capacity of the compressor can be maximized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a system diagram of a screw compressor according to an embodiment of the present invention. The screw compressor includes a compressor body 3 that compresses air, a motor 2 that drives the compressor body 3, and an inverter 1 that supplies desired power to the motor 2 to control the rotation speed of the motor 2. And a pressure sensor 7 which is a discharge air pressure detection means for detecting the pressure of the discharge air discharged from the compressor body 3, and the compressor 1 by controlling the operation of the inverter 1 based on the pressure detection value of the pressure sensor 7. And a rotation speed control device 8 that adjusts the amount of air discharged from the main body 3.

  Further, the present screw compressor includes a discharge pressure setting device 10 that determines a discharge pressure setting value that is a desired reference value of the discharge air pressure discharged from the compressor body 3, and the motor 2 according to the discharge pressure setting value. And a maximum rotational speed control device 9 for determining the maximum rotational speed. In addition, this screw compressor is also provided with the oil separator, the air cooler 5, and the discharge piping 6 which are demonstrated below.

  Next, the operation of the present screw compressor will be described. First, electric power is supplied from the inverter 1 to rotate the motor 2, and the compressor body 3 is driven by the rotation of the motor 2.

  The air compressed to a predetermined pressure by the compressor body 3 enters the oil separator 4 together with the lubricating oil mixed in the compression process. The compressed air separated from the lubricating oil here is discharged to the outside through the air cooler 5 and the discharge pipe 6.

  A pressure sensor 7 provided in the discharge pipe 6 detects the pressure of the compressed air and feeds back the detected value to the rotation speed control device 8. The rotation speed control device 8 calculates an operation rotation speed corresponding to the amount of compressed air used by demand equipment and controls the inverter 1 based on the calculated value to control the rotation speed of the motor 2.

  Here, the control range of the operating rotational speed is based on the pressure set by the discharge pressure setting device 10 and the rotational speed set in the maximum rotational speed control device 9 in advance as an upper limit.

  FIG. 2 is a graph showing the operable range of the screw compressor according to the discharge pressure set value and the rotation speed ratio. The inside of the trapezoid shown on this graph is an operable range. For example, assuming that the maximum rotation speed when the discharge pressure set value is the rated value 0.83 MPa is 100%, the upper limit of the maximum rotation speed is increased as the discharge pressure set value is decreased.

  In other words, the maximum rotation speed control device 9 determines the maximum rotation speed of the motor substantially in inverse proportion to the discharge pressure set value.

  In this example, when the discharge pressure set value is lowered to 0.59 MPa, the maximum rotational speed is 120% compared to the above-mentioned 0.83 MPa.

  On the other hand, in the conventional screw compressor, the maximum rotation speed of the compressor is fixed even when the set pressure value of the discharge air pressure detecting means is changed. For example, the discharge pressure set value of the compressor is 0.83 MPa. The maximum rotational speed of the compressor is the same in both the case and the case of 0.59 MPa. When the set pressure value is 0.59 MPa, the maximum rotational speed of the motor 2 is 20% lower than that of the screw compressor. It will be suppressed to.

  That is, the operating range of the present screw compressor is a trapezoidal range surrounded by points a, b, c, and d in FIG. 2, whereas the operating range of the conventional screw compressor is the point a, There is only a rectangular range surrounded by j, c, and d.

  By these, this screw compressor is the screw compressor which controls the number of rotations of the compressor body according to the amount of air used by the demand equipment, by setting the maximum number of rotations according to the discharge pressure set value, When a pressure lower than the rated pressure is set, an air volume exceeding the rated air volume can be obtained within the range of the motor load capacity, and the discharge pressure drop that occurs when the rated air volume is exceeded should be prevented. Can do. Here, the rated value is a representative value in the product specification.

FIG. 3 is a graph showing an example of operating characteristics of the maximum rotation speed control device 9 in the screw compressor. As shown in this graph, the relationship between the discharge pressure setting value P and the maximum rotation speed ratio x is
P = ax + b
It can be expressed by the following formula. Here, the constant a is a value determined according to the rated value of the set pressure, and the constant b is a value determined according to the lower limit value of the set pressure value.

  Further, the relationship between the discharge pressure setting value P and the maximum rotation speed ratio x is not limited to the above formula, and for example, various discharge pressure setting values P and the maximum rotation speed ratio x corresponding to each of the discharge pressure setting values P Data indicating the relationship may be preset in a memory or the like.

FIG. 4 is a graph showing a specific example of the operating characteristics of the maximum rotational speed control device 9, wherein the rated value of the set pressure is 0.83 MPa and the lower limit value is 0.59 MPa. From this, the relationship between the discharge pressure set value P and the maximum rotational speed ratio x is
P = −0.012x + 2.03
It can be expressed by the following formula.

  As described above, according to this embodiment, since the operating range of the compressor is wide, when the discharge pressure setting value of the compressor is lowered, the amount of air used on the compressor output side exceeds the conventional rated value. Even if it increases, the capacity of the compressor can be maximized and the discharge pressure of the compressor can be prevented from decreasing.

It is a systematic diagram of the screw compressor concerning an embodiment of the invention. It is a graph which shows the operation possible range in the screw compressor concerning an embodiment of the invention. It is a graph which shows an example of the operating characteristic of the maximum rotation speed control apparatus which concerns on embodiment of this invention. It is a graph which shows the specific example of the operating characteristic of the maximum rotation speed control apparatus which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inverter 2 Motor 3 Compressor body 4 Oil separator 5 Air cooler 6 Discharge piping 7 Pressure sensor 8 Rotational speed control device 9 Maximum rotational speed control device 10 Discharge pressure setting device

Claims (2)

A compressor body for compressing air;
A motor for driving the compressor body;
An inverter for supplying desired power to the motor to control the rotational speed of the motor;
Discharge air pressure detection means for detecting the pressure of discharge air discharged from the compressor body;
A discharge pressure setting means for determining a discharge pressure set value that is a desired reference value of the pressure of the discharge air discharged from the compressor body;
When the discharge pressure setting value is set lower than the rated pressure, the maximum rotation speed larger than the maximum rotation speed when the discharge pressure setting value is set to the rated pressure is set within the load capacity range of the motor. Maximum speed control means to
When the discharge pressure set value is set lower than the rated pressure, the maximum revolution speed control means is preset based on the discharge pressure set value set lower than the rated pressure by controlling the inverter. While controlling the discharge pressure to be the discharge pressure set value set by the discharge pressure setting means based on the pressure detection value detected by the discharge air pressure detection means within a range with the maximum rotation speed as the upper limit, A rotational speed control means for controlling the rotational speed of the motor in accordance with a change in the amount of air used in the discharged air;
A screw compressor characterized by comprising: The screw compressor according to claim 1,
The screw compressor according to claim 1, wherein the maximum rotation speed control means sets the maximum rotation speed independently of the pressure detection value.

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