JP2968189B2 - Operating method of compressor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of operating a compressor for adjusting an intake air amount and controlling an on / off operation by an intake air control valve.

[0002]

2. Description of the Related Art Conventionally, Japanese Unexamined Patent Publication No.
In the oil-cooled compressor, an operation method of the oil-cooled compressor is disclosed in which the pressure in the discharge passage is kept within a certain range by using both the intake capacity control valve control and the on / off control. . Specifically, this operation method is based on the detection pressure per unit time obtained from the pressure detected by the first pressure sensor provided in the discharge flow path of the compressor body and the pressure detected by the second pressure sensor provided in the suction flow path. Based on the compressed gas supply amount and the predetermined volume of the gas flow space portion, calculate the compressed gas usage amount,
Assuming that there is no new gas supply, calculate the time required for the pressure in the gas flow space to drop to the lower limit set value. It is possible to stop.

[0003]

In the above conventional method of operating an oil-cooled compressor, the lower limit set value of the pressure in the compressed gas flow space is constant. In a compressor having a long time from the start to the supply of the compressed gas, the pressure can sufficiently fall below the lower limit set value. For this reason, when setting the lower limit set value, in addition to the pressure necessary for practical use, the pressure drop and the pressure fluctuation before the compressed gas supply are taken into consideration, and the lower limit set value with sufficient margin is set. There is a problem that needs to be determined. SUMMARY OF THE INVENTION The present invention has been made to solve such a conventional problem, and has been made in consideration of a compression method capable of performing on-off control in which a pressure in a discharge flow path which is a compressed gas flow space does not fall below a lower limit set value. It is intended to provide a method of operating the machine.

[0004]

In order to solve the above-mentioned problems, according to the present invention, a detection pressure P (t) detected by a pressure detector provided in a discharge passage of a compressor body increases, and an upper limit set pressure P
When the pressure reaches H, the intake control valve provided in the suction flow passage of the compressor body closes to shift to a no-load operation state, and the compressor operates in an on-off control operation state. In advance, the required pressure feeding time T, which is the time until the compressed gas starts to be discharged, is set in advance, and when the operation shifts to the no-load operation, the detected pressure P (t)
Among them, the average pressure gradient p is calculated based on the detected pressure sampled at regular time intervals, and the compressor main body is stopped based on the calculated average pressure gradient p, the above-described required time T for pumping and the lower limit set pressure PL. Thereafter, at the time of restart, the restart pressure P (T) at which the detected pressure P (t) does not become lower than the lower limit set pressure PL before the required time T for pumping elapses is calculated. Starting pressure P
A restart time tR, which is a time required to fall to (T), is calculated, and the restart time tR is set to be equal to or longer than a predetermined time set as a time interval in which the stop and restart of the compressor body are allowed to be repeated. If it is, stop the compressor body,
If it is shorter, the no-load operation is continued while repeating the above calculation, and the detected pressure P (t) is maintained even after the compressor body is stopped.
Of which, the detected pressure sampled and the time required for pumping T
And a new restart pressure P 'based on the lower limit set pressure PL
(T), the average pressure gradient p 'is calculated and updated so that it can follow changes in the amount of air used.

[0005]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a compressor to which the operation method according to the present invention is applied, for example, a screw compressor. The screw compressor includes an intake control valve 3 in a suction flow path 2 of a compressor body 1 and a discharge flow path 4. Is provided with a pressure detector 5 provided to detect pressure. Further, upon receiving a pressure signal from the pressure detector 5, the compressor body 1
Control means 7 for controlling the driving section 6 of the camera as described in detail below.
Is provided.

Next, the operation method according to the present invention will be described by applying to the compressor. As shown in FIG. 2, first, in step 1 (S1), the compressor body 1 is started, and the following control is started. In step 2 (S2), at the same time when the compressor main body 1 is started, a predetermined time determined from the allowable start frequency, for example, 1
Start the timer set for 5 minutes. It is necessary to limit the starting frequency based on the load and heat capacity of the motor that starts the compressor body 1, and if the starting frequency exceeds the allowable starting frequency, the motor will be burned. For this reason, after the compressor body 1 is started, the motor is not stopped until the predetermined time set in the timer elapses, thereby protecting the motor.

In step 3 (S3), it is determined whether or not the pressure P (t) detected by the pressure detector 5 is equal to the upper limit set pressure PH. If YES, the process proceeds to step 4 (S4), and if NO, Repeats the above determination. Step 4 (S
In 4), it is determined whether or not the time of the timer has elapsed 15 minutes, that is, whether or not 15 minutes have elapsed after the start of the compressor body 1. If YES, the process proceeds to step 5 (S5).
If NO, the process returns to step 3. As described above, frequent starting and stopping of the electric motor are prevented, and the electric motor is not burned.

In step 5 (S5), sampling of the detected pressure by the pressure detector 5 is performed for a fixed time, for example, one minute. When the detected pressure P (t) reaches the upper limit set pressure PH, the intake control valve 3 automatically closes, and the compressor body 1
Is set to a state of zero or almost equal to zero. Such an intake control valve 3 itself is well known.
Therefore, the detected pressure sampled in step 5 decreases as time elapses. The solid line A in FIG. 3 shows an example of the state of the pressure change in such a case. In step 6 (S6), 1
Based on the data obtained during the minute, as described below, the average pressure gradient p of the descending pressure and the restart pressure P
(T) and the restart time tR are calculated.

Even if the compressor is restarted, the gas compression does not immediately start, but the non-load operation (the state of the discharge gas amount is zero) is continued for a fixed time, that is, for the required time T for pumping.
Thereafter, the gas compression is gradually started, and the compressed gas is discharged to the discharge flow path 4. That is, after the restart, it takes a time T required for pumping, for example, about 25 seconds, to discharge the compressed gas. If the compressor body 1 is stopped, the consumption of the compressed gas from the discharge passage 4 continues, and the compressor body 1 is restarted only when the pressure in the discharge passage 4 reaches the lower limit set pressure PL. For example, it is necessary to elapse the required time T for the pressure feeding until the compressed gas is actually discharged. During this time, the pressure in the discharge flow path 4 continues to decrease. As a result, there arises a problem that the pressure in the discharge channel 4 becomes lower than the lower limit set pressure PL. In order to prevent such a situation from occurring, at least the time required for pumping T exceeds the time when the pressure in the discharge flow path 4 predicted from the calculated average pressure gradient p will reach the lower limit set pressure PL. It is necessary to restart the compressor body 1 as soon as possible.

In the case of the example shown in FIG. 3, it is predicted that the pressure will drop from the calculated average pressure gradient p as shown by a two-dot chain line B, and the pressure will be pumped before the time when this pressure will reach the lower limit set pressure PL. The compressor body 1 is restarted earlier by the required time T. The pressure P (T) at the time of restart thus obtained is referred to as a restart pressure, and the time tR from the end of sampling to the restart is referred to as a restart time. Specifically, the calculation of each value in step 6 is obtained by the following equation.

(Equation 1)

In step 7 (S7), the restart time tR
Is determined to be a predetermined time, for example, 1 minute or more. If YES, the process proceeds to Step 8 (S8), and if NO, this determination is repeated. Here, when the restart time tR is 1 minute or more, the process proceeds to step 8. The reason for restarting the compressor body 1 at a very short time interval is that the pressure on the discharge side of the compressor body discharges to the atmosphere. Start up in a state where it cannot be removed (residual pressure start up)
This causes a start in an overload state, and the start becomes impossible.

In step 8 (S8), the compressor body 1 is stopped. That is, a sufficient time can be secured before the pressure in the discharge flow path 4 reaches the upper limit set pressure PH and restarts.
Since there is no problem in cooling the compressor main body 1, the compressor main body 1 is stopped. Step 9
In (S9), similarly to step 5, sampling of the detected pressure by the pressure detector 5 is performed for a fixed time, for example, 1 minute. In step 10 (S10), the average pressure gradient p 'of the pressure descending and the restart pressure P' (T) are calculated based on the data obtained during one minute after the start of sampling in the same manner as in step 6. I do. Step 11 (S11)
Then, the previously determined restart pressure P (T) is updated to the restart pressure P ′ (T) calculated after the stop. This is to determine the restart pressure following the change in the air usage.

In step 12 (S12), the restart pressure P is updated when the pressure P (t) detected by the pressure detector 5 is updated.
It is determined whether or not it is equal to (T). If the determination is YES, the process proceeds to step 13 (S13). If the determination is NO, the process proceeds to step 9 to newly perform pressure sampling. Step 13 (S
In 13), since there is no problem even if the compressor main body 1 is restarted, the compressor main body 1 is restarted, and thereafter, the process returns to step 2 and the above control is repeated. As described above, the restart pressure is calculated and the restart pressure is updated based on the pressure detected by the pressure detector 5, so that the on / off control of the compressor is performed. The pressure in the discharge flow path 4 does not become lower than the lower limit set pressure, and the pressure in the discharge flow path 4 is always maintained within an appropriate range.

[0014]

As is apparent from the above description, according to the present invention, the pressure P (t) detected by the pressure detector provided in the discharge passage of the compressor body increases, and reaches the upper limit set pressure PH. Upon reaching, the intake control valve provided in the suction passage of the compressor body is closed to shift to the no-load operation state, and the compressor is operated in the on-off control operation state. The required pressure feeding time T, which is the time until the gas starts to be discharged, is set in advance, and when the operation shifts to the no-load operation, the detection pressure P (t)
The average pressure gradient p is calculated based on the detected pressure sampled at regular time intervals, and in addition to the calculated average pressure gradient p,
On the basis of the above-mentioned required time T and the lower limit set pressure PL,
After the compressor body is stopped, when the compressor is restarted, the detected pressure P (t) does not become lower than the lower limit set pressure PL until the required pressure feeding time T elapses.
(T) is calculated, and a restart time tR, which is a time required until the pressure drops to the restart pressure P (T), is calculated. The compressor main body is stopped when it becomes equal to or more than a predetermined time set as an allowable time interval, and when it is short, the above-described calculation is repeated to continue the no-load operation, and the detected pressure is maintained even after the compressor main body is stopped. Among the P (t), the restart pressure P ′ (T) is newly determined based on the sampled detected pressure, the required time T for pumping, and the lower limit set pressure PL.
The average pressure gradient p 'is calculated and updated so that it can follow changes in the amount of air used. For this reason, there is an effect that it is possible to perform on / off control in which the pressure in the discharge flow path that is the gas flow space does not fall below the lower limit set value.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating an overall configuration of a compressor to which an operation method according to the present invention is applied.

FIG. 2 is a flowchart showing a control procedure in the driving method according to the present invention.

FIG. 3 is a diagram illustrating a relationship between a pressure in a discharge flow path and an elapsed time when an operation method according to the present invention is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Compressor main body 2 Suction flow path 3 Intake control valve 4 Discharge flow path 5 Pressure detector 6 Drive unit 7 Control means

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F04B 49/00-51/00

Claims (1)

(57) [Claims] 1. A pressure P (t) detected by a pressure detector provided in a discharge flow path of a compressor body increases, and an upper limit set pressure P
When the pressure reaches H, the intake control valve provided in the suction flow passage of the compressor body closes to shift to a no-load operation state, and the compressor operates in an on-off control operation state. In advance, the required pressure feeding time T, which is the time until the compressed gas starts to be discharged, is set in advance, and when the operation shifts to the no-load operation, the detected pressure P (t)
Among them, the average pressure gradient p is calculated based on the detected pressure sampled at fixed time intervals, and the compressor main body is stopped based on the calculated average pressure gradient p, the above-mentioned required time T and the lower limit set pressure PL. Thereafter, at the time of restart, the restart pressure P (T) at which the detected pressure P (t) does not become lower than the lower limit set pressure PL before the required time T for pumping elapses is calculated. Starting pressure P
A restart time tR, which is a time required to fall to (T), is calculated, and the restart time tR is set to be equal to or longer than a predetermined time set as a time interval in which the stop and restart of the compressor body are allowed to be repeated. If it is, stop the compressor body,
If it is shorter, the no-load operation is continued while repeating the above calculation, and the detected pressure P (t) is maintained even after the compressor body is stopped.
Of which, the detected pressure sampled and the time required for pumping T
And a new restart pressure P 'based on the lower limit set pressure PL
(T) A method of operating a compressor, characterized in that an average pressure gradient p 'is calculated and updated so as to be able to follow a change in air usage.