JPH0350117B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a predictive input control circuit for controlling a compressor.

[Background of the invention]

A conventional technique for controlling the number of compressors will be explained with reference to FIG. 1 and FIG. 3.

Conventionally, when controlling the number of compressors, when the air volume used on the load side increases and the pressure on the load side decreases and reaches the pressure drop point shown in Figure 1, the stopped compressor is started. , bring the load side pressure closer to the control target pressure M. Conversely, when the air volume used on the load side decreases, the load side pressure increases, and when it reaches the pressure rise point, the operating compressor is stopped to bring the load side pressure closer to the control target pressure M. . This operation is repeated to control the load side pressure within a certain range around the control target pressure M shown in FIG. 1.

However, in order to protect the compressors, the starting frequency is limited, and in order to prevent overcharging and overstopping, consideration has been given to starting and stopping each compressor after a certain time limit.

In the load side usage air volume characteristics as shown in FIG. 2, if the usage air volume on the load side increases rapidly at time T, the load pressure suddenly decreases as shown in FIG.
When the load pressure reaches the pressure drop point L, one of the compressors is activated.

In principle, the compressor starts without load, and the compressor can start and supply compressed air to the load side about 10 seconds after startup, and during that time, the pressure on the load side will decrease.
The pressure continues to drop further, and the stopped compressor is additionally started again. In this way, the compressor is repeatedly started until the load side pressure becomes equal to or higher than the pressure drop point L. In the characteristics of the number of compressors in operation in Figure 3, the time T
The number of additional compressors in operation after that was 4.

When the load side pressure becomes equal to or higher than the pressure drop point L due to compressor operation, the compressor start command is canceled, but in order to deal with the sudden load air volume on the load side,
As the number of compressors in operation exceeds the required number, resulting in overloading, the load-side pressure naturally continues to rise, and this time, conversely, the load-side pressure reaches the pressure rise point H.
That's all.

A stop command is issued to the compressor that is in operation, but to protect the induction motor that drives the compressor, once it has started, it cannot be stopped for a certain period of time, so it cannot be stopped immediately and the excess compressor It will continue to be operated for a certain period of time.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a predictive input control circuit that prevents a drop in pressure on the load side and excessive operation of the compressor in response to a sudden increase in the amount of air used on the load side.

[Summary of the invention]

The time T shown in FIG. 2 during which the air volume used on the load side rapidly increases can be set at a time such as at the start of production operation, and the required number of compressors can be easily determined from the amount of equipment operation.

This time T and the required number of compressors are set using a schedule timer, etc., and the required number of compressors are operated before the time T when the air volume used on the load side suddenly increases, thereby ensuring pressure on the load side. , it becomes possible to prevent excessive operation of the compressor.

In addition, if the compressor is operated before the time T when the air volume used on the load side suddenly increases, the load side pressure will rise, and it will be necessary to temporarily lock the stop command to the compressor to prevent the compressor from stopping. However, this lock release is performed based on the pressure drop condition after a sudden increase in the amount of air used on the load side.If the lock release is performed using a schedule timer, there may be a problem due to a setting error (if time T is delayed, the compressor may be under load). Consideration has been given to eliminating the possibility of the system shutting down before or during a sudden increase in air usage.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 4 to 8.

First, a schedule timer or the like is used to set the time T at which the usage air volume on the load side suddenly increases, and the time t required for the required number of operating compressors to operate, as shown in FIG.

Now, in FIG. 5, the number of compressors is controlled until time Tt, as explained in the prior art, so that the load side pressure approaches the control target pressure. As is clear from Figures 5 and 6, if the air volume used on the load side increases so that the number of operating compressors matches the air volume used on the load side, the load side pressure will reach the pressure drop point L. reached, and one compressor starts. Moreover, if the air volume used on the load side decreases, the load side pressure rise point H is reached and one compressor stops.

When the time reaches Tt, the compressors are forced to operate regardless of the load side pressure by the predicted input command, and the required number of compressors are operated during the time t.

FIG. 7 shows a predictive input control circuit for a plurality of compressors, and is configured as follows.

When the schedule timer T24 provided in the timer setting circuit operates, the first contact T24X1 of the energized amplification relay T24X is closed, and the compressor start command relay LX in the low pressure circuit is energized for a period of time t, forcibly reducing the pressure. Apply signal LX′ to operate the required number of compressors.

At this time, in order to prevent the pressure increase signal HX' of the pressure increase circuit from being output, that is, to prevent the pressure increase relay HX from being energized,
Close 4X2. Note that the first and second contacts are closed only for the time set by the timer. Second contact T24
When X2 is closed, the lock relay TN provided in the lock circuit is energized, and the lock contact TNb, which is the B contact of the lock relay TN, is open only for a time t, that is, while the load usage is increasing. Therefore, during this time, the lock contact provided in the pressure increase circuit
Open TNb and forcibly lock it so that the pressure increase signal HX' is not output from the pressure lock circuit.

If the lock timer TN is installed in the input prediction control circuit,
If the lock contact TNb is not provided, the compressor is being operated redundantly, so the load side pressure naturally increases, and the pressure rise point H in Figure 5.
As a result, the compressor that was operating before the predicted injection stops due to the pressure increase.

In this way, preparations are made to respond to a sudden increase in air usage, and when time T arrives, the compressor is operating in time to meet the air usage on the load side, so the load side pressure is reduced to the pressure drop point. without letting
It becomes possible to follow.

When the time T has passed, the air flow rate used on the load side increases rapidly, so that the load side pressure, which has been above the pressure rise point H, falls below the pressure rise point H. Under these conditions, as shown in the time chart of Figure 8,
By de-energizing the TN relay, it is possible to release the lock on the compressor stop command after the predicted turn-on and return to the original control state.

This unlocking of the compressor stop command may be set in advance using the schedule timer T24, but if the load-side usage air volume increase point T is delayed, the lock of the stop command will be released earlier in time, and the load If this occurs before the side air flow increases rapidly, the compressor will stop. Taking this risk into consideration, the present invention uses pressure to monitor and release the lock.

〔Effect of the invention〕

According to the predictive power supply control circuit of the present invention, by providing a lock timer TN, a lock contact TNb, etc. in this circuit, the compressor is operated redundantly, so the load side pressure naturally increases.
Since the pressure rises above the pressure rise point H in FIG. 5, it is now possible to prevent the compressor that was operating before the predicted injection from stopping due to the pressure rise. Therefore, the load-side pressure is not lowered below the usable pressure, energy is saved compared to conventional control, and the control system can be stabilized.

Further, since a lock timer and a lock contact may be provided in the predictive input control circuit, it can be realized with a simple circuit.

[Brief explanation of drawings]

Figure 1 is a conventional load-side pressure-time characteristic diagram, Figure 2
Figure 3 shows the compressed air load side used air volume vs. time characteristic diagram, Figure 3 shows the conventional number of operating compressors vs. time characteristic diagram, Figure 4 shows the predicted injection command of the present invention vs. time characteristic diagram, and Figure 5 shows the time characteristic diagram.
Figure 6 is a load side pressure-time characteristic diagram of the present invention, Figure 6 is a compressor operation number-time characteristic diagram of the present invention, Figure 7 is an electric circuit diagram of an embodiment of the present invention, and Figure 8 is a diagram of the time characteristic diagram. 7
This is a time chart. HX...Pressure increase relay, T24X...Amplification relay.

Claims (1)

[Claims] 1 A schedule timer setting circuit, a pressure reduction circuit, a pressure increase circuit, and a lock circuit are connected in parallel to a control circuit that predictably turns on multiple compressors, and when the schedule timer is set in the timer setting circuit, the excitation is activated. an amplifying relay, the pressure reducing circuit and the locking circuit having first and second contacts that close when the amplifying relay is energized;
When the contact closes, a compressor start command relay is installed in the low pressure circuit that gives a start command to the compressor and forcibly reduces the pressure of the compressor, and when the second contact closes, the load usage of the lock circuit increases. Predictive start-up of an air compressor characterized in that a locking relay is provided which is energized only for a certain period of time, and when the locking relay is energized, a locking contact of a pressure increasing circuit is opened and the pressure increasing circuit is forcibly locked. control circuit.