JP5232412B2 - Directly connected water supply system - Google Patents

Description

  The present invention relates to a direct-coupled water supply apparatus, and more particularly to a direct-coupled water supply apparatus that operates a plurality of pumps connected to a water main in parallel.

  A water supply device is installed in an apartment house or a building and supplies water to each water supply end. FIG. 1 shows a typical example of such a water supply apparatus. The water supply apparatus includes two motor pumps 1 and an inverter (frequency converter) 2 for supplying electric power for driving the two motor pumps 1. I have. The water supply device includes a pressure tank 3 and a discharge-side pressure sensor 4 on the discharge side of the pump 1, and a flow switch (flow rate detection means) 6 and a check valve 7 for each pump. A suction side pipe 8 of the pump is connected to a water main pipe 9, and a suction side pressure sensor 10 and a backflow prevention device 11 are provided in the suction side pipe 8. Further, a bypass pipe 12 for supplying water only with the pressure of the water main pipe is provided between the suction side pipe 8 and the discharge side pipe 13 of the pump 1. A check valve 14 is provided in the middle of the bypass pipe 12. The control device 15 that controls the motor pump 1 performs the rotational speed control and the number control of the pump 1 according to the situation based on signals from these sensors.

  FIG. 2 is a QH diagram when performing such constant control of the estimated terminal pressure of the water supply apparatus, the horizontal axis indicates the flow rate Q, and the vertical axis indicates the pressure (head) H. The minimum required pressure PB of the water supply system and the required pressure PA at the maximum demand water volume are connected by a resistance curve R of the pipe line depending on the flow rate, and the pressure indicated by the resistance curve R at each flow rate is the target pressure to be supplied by the water supply device It becomes. The minimum required pressure PB of the water supply system and the required pressure PA at the maximum demand water amount are previously set and stored in the control device 15 by the setting means. The control device 15 issues a rotational speed command to the inverter 2 between the pump rotational speed HzB at which the pressure becomes PB in the closed state and the pump maximum rotational speed HzMax, but estimates the flow rate from the current pump rotational speed command value. The target pressure at that time is determined, and a rotation speed command is issued to the inverter 2 so that the pressure detected by the discharge-side pressure sensor 4 matches the target pressure.

  In the water supply apparatus configured as described above, when water is used on the demand side while the pump is stopped and the detected pressure of the discharge-side pressure sensor 4 falls below the starting pressure (minimum required pressure) PB, the control device 15 causes the pump 1 Activate one. In this case, the pump 1 is operated at a pump speed HzB. When the demand water volume increases, the pump 1 increases the rotation speed from the pump rotation speed HzB to Hz1, Hz2,..., But when the flow rate exceeds Q1, the pump rotation speed reaches the maximum rotation speed HzMax. As a result, the target pressure cannot be satisfied. Therefore, when the pump rotation speed command reaches the maximum rotation speed HzMax, another pump is started. At this time, the pump that was started first (the first pump) is fixed at a predetermined speed HzMax ′ whose operating speed is slightly lower than the maximum speed HzMax, and becomes a fixed speed pump. It becomes a variable speed pump that is controlled at variable speed according to the amount of demand water, and satisfies the target pressure. The fixed speed pump is operated at a predetermined number of revolutions determined in advance, regardless of fluctuations in the discharge pressure.

If the demand water volume decreases while two pumps are operating, the number of revolutions of the later pump will be reduced. However, if the water volume is Q1 or less, the demand can be met with one pump. Stop. The control device 15 detects that the amount of water supplied from the subsequent pump is small by the flow switch 6 of the subsequent pump, stops the subsequent pump from being disconnected, and controls the preceding pump again at a variable speed.
When the demand water volume further decreases, the rotational speed of the starter pump is lowered, but when the flow switch 6 of the starter pump detects that the amount of water is small, the control device 15 also stops the starter pump and uses the water again. The standby state is maintained until the detected pressure of the discharge side pressure sensor 4 becomes equal to or lower than the starting pressure (minimum required pressure) PB.

  Moreover, in the direct connection type water supply apparatus, the pressure of the water main pipe is applied to the pump suction side, and the pressure also fluctuates. When the suction pressure increases, the same pressure and flow rate can be covered at a lower pump rotation speed, so the relationship between PB and HzB described above changes. For this reason, the relationship between the target pressure and the pump rotation speed command is appropriately corrected according to the suction pressure, and appropriate estimated terminal pressure constant control is performed. If the suction pressure is further increased and exceeds the target pressure, water can be supplied without driving the pump, so the control device 15 stops the pump. When the suction pressure decreases and falls below the target pressure, the pump is driven again.

JP-A-9-268978 JP 2003-21069 A Japanese Patent Laid-Open No. 5-118280

  In the estimated terminal pressure constant control, the target pressure at that time is determined based on the rotational speed command value of the pump as described above. In the situation where two pumps are operating, if the suction pressure does not vary, the performance curve of the starting pump that operates at a fixed speed will not vary, but the suction pressure varies in the direct-coupled water supply system. In addition, stable terminal pressure constant control cannot be performed without taking account of fluctuations in the suction pressure.

  Also, when the water main pressure rises and water can be supplied only with the water main pressure, the pump is stopped. At this time, the water mainly flows through the bypass pipe, and there is a pump, etc. The amount of water flowing through the pipe where the pump is installed is small. For this reason, even when the demand water volume is large and the two pumps are operating, if the water main pressure rises and water is supplied only with the water main pressure, the flow switch of the later pump is small. The amount of water is detected and the operation is shifted to the operation of only one pump. After that, when the water main pressure drops and the detection pressure of the discharge-side pressure sensor falls below the target pressure, the pump starts rotating again, but the suction pressure declines suddenly and the demand water volume remains large. In such a case, it is impossible to cover a single pump, and a new pump must be added. As a result, the discharge pressure fluctuates, which may make the consumer feel uncomfortable.

  The present invention has been made in view of the above circumstances, and includes a plurality of variable speed motor pumps that are operated in parallel, and can perform stable control with little pressure fluctuation due to fluctuations in suction pressure during parallel operation. It aims at providing a direct connection type water supply apparatus.

In order to achieve the above-described object, a first aspect of the present invention includes a plurality of pumps connected to a water main, a plurality of frequency converters that respectively shift the pumps, a discharge-side pressure sensor, A suction-side pressure sensor and a control device that controls these devices, and is a direct-coupled water supply device that operates a plurality of pumps in parallel, the control device according to the detected pressure of the discharge-side pressure sensor Parallel operation is performed with a variable speed pump that is operated at a variable speed and a fixed speed pump that is operated at a predetermined speed, the suction pressure is reduced , the frequency command value to the variable speed pump is not 0 Hz, and the number of variable speed pumps is small. When the water amount is present, the shift pump is stopped.
Here, the fixed speed pump refers to a pump that is operated at a predetermined rotation speed that is not related to the fluctuation of the discharge pressure, and does not prevent the predetermined rotation speed from being changed by factors other than the fluctuation of the discharge pressure.

  According to a second aspect of the present invention, a plurality of pumps connected to a water main, a plurality of frequency converters that respectively shift the pumps, a discharge side pressure sensor, a suction side pressure sensor, and these devices A direct-connection water supply device that operates a plurality of pumps in parallel, the control device being operated with a speed change pump in accordance with a pressure detected by the discharge side pressure sensor and a predetermined speed When parallel operation is performed with a fixed speed pump operated at a speed and the pump is stopped due to an increase in suction pressure during parallel operation, the stop condition between the transmission pump and the fixed speed pump is given a difference. When the speed change pump is stopped first and the pump is restarted due to a decrease in suction pressure, the fixed speed pump is restarted in advance before the speed change pump is restarted.

  In a preferred aspect of the present invention, the control device has a first pressure set value and a second pressure set value that is higher than the first pressure set value. When the detected pressure exceeds the first pressure set value, the transmission pump is stopped, and when the detected pressure exceeds the second pressure set value, the fixed speed pump is stopped and the suction pressure is reduced to reduce the suction side pressure sensor. When the detected pressure falls below the second pressure set value, the fixed speed pump is restarted.

According to a third aspect of the present invention, there are provided a plurality of pumps connected to a water main, a plurality of frequency converters for shifting the pumps, a discharge-side pressure sensor, a suction-side pressure sensor, and these devices. A direct-connection water supply device that operates a plurality of pumps in parallel, the control device being operated with a speed change pump in accordance with a pressure detected by the discharge side pressure sensor and a predetermined speed When performing parallel operation with a fixed speed pump operated at a speed, and restarting the pump due to a decrease in suction pressure after stopping the transmission pump and the fixed speed pump due to an increase in suction pressure during parallel operation, The fixed speed pump is restarted in advance before restarting the transmission pump.
In a preferred aspect of the present invention, the fixed speed pump is operated at a speed set in accordance with a pressure detected by the suction side pressure sensor.

In a preferred aspect of the present invention, the control device sets the speed of the fixed speed pump that is set according to the pressure detected by the suction side pressure sensor, so that the cutoff pressure at the speed is constant regardless of the fluctuation of the suction pressure. It sets so that it may become.

According to the present invention, a plurality of variable speed motor pumps operated in parallel are provided, and stable control with little pressure fluctuation can be performed even by fluctuations in suction pressure during parallel operation.
More specifically, the following effects are obtained.
(1) According to one aspect of the present invention, when the suction pressure rises and the pump is stopped, the parallel operation is canceled and the subsequent pump is operated at a variable speed so as not to stop the parallel pump. If the frequency command value to the pump is 0 Hz, or if the suction pressure is PA or higher, or HzB (frequency at which the cutoff pressure at that time is the minimum required pressure PB of the water supply system) is 0 In some cases, control is performed such that the disconnection operation is not performed.
(2) According to one aspect of the present invention, when the pump stops due to an increase in suction pressure during parallel operation, there is a difference in the stop conditions between the pump during variable speed operation and the pump during fixed speed operation. The pump during variable speed operation is stopped first, and even when the pump is restarted due to a decrease in suction pressure, the fixed speed pump starts in advance before the discharge pressure falls below the target pressure, thus suppressing pressure fluctuations. Stable water supply becomes possible.
(3) According to one aspect of the present invention, when the suction pressure rises during the parallel operation of the pumps and becomes equal to or higher than the first pressure set value, the subsequent pump that is performing the shifting operation is stopped. Continue operation of the starting pump. When the suction pressure decreases and the discharge pressure falls below the target pressure, the subsequent pump is restarted. However, when the suction pressure further increases and exceeds the second pressure set value, the preceding pump is also stopped. When all the pumps are stopped, if the suction pressure falls below the second pressure set value, the first pump is restarted.If the discharge pressure falls below the target pressure, the second pump is restarted in the shift operation. The Therefore, when restarting a plurality of pumps, stable water supply with suppressed pressure fluctuation becomes possible.
(4) According to one aspect of the present invention, during the parallel operation, the speed change pump is speed-changed and the fixed speed pump is operated at a speed set according to the suction pressure. Stable end pressure constant control in consideration of fluctuations can be performed.

[First Embodiment]
FIG. 3 is a schematic configuration diagram of the direct-coupled water supply apparatus according to the first embodiment of the present invention. In FIG. 3, the same components as those in FIG. In the direct connection type water supply apparatus shown in FIG. 3, the three pumps 1 are provided, and each is connected in parallel. Corresponding to each pump 1, an inverter (frequency converter) 2 for supplying electric power for driving each pump 1 is provided. The water supply apparatus includes a pressure tank 3 and a discharge-side pressure sensor 4 on the discharge side of the pump, and includes a flow switch (flow rate detection means) 6 and a check valve 7 for each pump. A suction side pipe 8 of the pump is connected to a water main pipe 9, and a suction side pressure sensor 10 and a backflow prevention device 11 are provided in the suction side pipe 8. Further, a bypass pipe 12 for supplying water only with the pressure of the water main pipe is provided between the suction side pipe 8 and the discharge side pipe 13 of the pump 1. A check valve 14 is provided in the middle of the bypass pipe 12.

  The control device 15 sets and stores the minimum required pressure PB of the water supply system, the required pressure PA at the maximum demand water amount, and the like by an external operation. The control device 15 and each inverter 2 are connected by communication means such as RS485, and control signals such as various set values, frequency command values, start / stop signals (start / stop signals) are transmitted from the control device 15 to the inverter 2. Thus, the operation status such as the actual frequency value and current value is sequentially sent from the inverter 2 to the control device 15. The control device 15 receives signals from sensors such as the discharge side pressure sensor 4, the suction side pressure sensor 10 and the flow switch 6, determines the start / stop of each inverter, and calculates the frequency command value. I do.

  FIG. 4 is a flowchart of the estimated terminal pressure constant control of such a water supply apparatus. First, the control device 15 takes in the detection pressure of the discharge side pressure sensor 4 and takes in the detection pressure of the suction side pressure sensor 10. Next, at the suction pressure at that time, the pump rotation speed HzB that is the minimum required pressure PB of the water supply system in the closed state is calculated. The control device 15 stores the relationship among the suction pressure, the pump cutoff pressure, and the pump rotation speed as table data or a function, and calculates the pump rotation speed HzB using this relationship. Further, the maximum operating frequency (maximum pump speed) HzMax at the suction pressure at that time is calculated. This maximum operating frequency HzMax is the rotation speed that becomes the pressure Pmax (see FIG. 5) when the cutoff operation is performed at the suction pressure at that time and the cutoff operation is performed at the maximum rotation speed of the pump when the suction pressure is zero. The above-described maximum operating frequency HzMax at the suction pressure at that time is also calculated using the table data or function indicating the relationship between the suction pressure, the pump cutoff pressure, and the rotation speed stored in the control device 15.

Next, the control device 15 calculates a target pressure for the estimated terminal pressure constant control based on the calculated HzB and the current frequency command value. Then, the calculated target pressure is compared with the current discharge pressure to calculate the frequency command value of the pump that is operating at a variable speed by PI calculation. If this frequency command value is smaller than HzB, the frequency command value is calculated. If it is larger, the calculated value is directly used as the frequency command value.
Next, it is confirmed whether or not two or more pumps are operating in parallel. If they are operating in parallel, the frequency command of the starting pump that is operated as a fixed speed pump is 95% of HzMax calculated in the above step. Specify the frequency. Then, it is finally confirmed whether or not this frequency command value does not fall below HzB. Here, 95% of HzMax is used, but as long as the frequency is lower than HzMax, a frequency obtained by multiplying HzMax by a predetermined ratio (not limited to 95%) or a frequency obtained by subtracting a predetermined value from HzMax may be used.

  Thus, the frequency command value of the pump 1 being operated is determined, and the control device 15 transmits the frequency command value to each inverter 2. Since HzMax varies depending on the suction pressure, the starting pump actually changes its operating frequency in accordance with the variation of the suction pressure, although it is a fixed speed pump. In other words, the fixed-speed pump here is a pump that has no relation to the comparison calculation between the discharge pressure and the target pressure, and changes the operating frequency only in response to fluctuations in the suction pressure. Due to this change in the operating frequency, the cutoff pressure at that frequency becomes constant regardless of the fluctuation of the suction pressure, that is, the performance curve of the starting pump becomes constant regardless of the suction pressure. The calculation of the target pressure is stable.

Next, the control when the suction pressure varies will be described with reference to FIG. In FIG. 5, the horizontal axis represents the operating frequency of the pump, and the vertical axis represents the pressure. PB and PA are the minimum required pressure of the water supply system and the required pressure at the maximum demand water volume, respectively, as in FIG. A curve C0 represents the relationship between the operating frequency of the pump when the suction pressure is 0 and the cutoff pressure at that time. The frequency of the intersection of the straight line with the constant pressure PB and the curve C0 is HzB, and the pressure at the maximum pump speed HzMax is Pmax.
Each of the curves C1 to C4 represents the relationship between the operating frequency of the pump when the suction pressure becomes Pin1 to Pin4 and the cutoff pressure at that time. As explained in FIG. 4, HzB and HzMax are updated by the fluctuation of the suction pressure, but the values are represented by the intersection of the curve in FIG. 5 and the straight line where the pressure is constant PB and Pmax. When the suction pressure is Pin1, HzB1 and HzMax1 are obtained. When the suction pressure rises to Pin2, the curve C2 and the straight line with a constant pressure PB do not cross each other, but HzB at this time is set as HzB2 = 0. When the suction pressure further increases and becomes Pin 4 higher than Pmax, the curve C4 does not intersect with a straight line with a constant pressure Pmax, but at this time, HzMax is set as HzMax4 = 0.

  Now, if two pumps are operating in parallel and the suction pressure is Pin1, the first pump is operated as a fixed speed pump at a frequency of HzMax1 × 0.95, and the second pump is operated at a variable speed at a frequency of HzB1 or higher. ing. If the suction pressure is increased to Pin3 in this state, the maximum value PA of the target pressure in the estimated terminal pressure constant control will be exceeded. Therefore, the calculation result of the command frequency for the subsequent pump that is operating at variable speed becomes 0 Hz, which is substantially Will stop. On the other hand, since the starting pump operated as a fixed speed pump is HzMax3 × 0.95> 0 Hz, the operation is continued. At this time, water supply is also performed through a bypass pipe. When the suction pressure further increases to Pin4, HzMax4 = 0, so the command frequency to the starting pump is also 0Hz, and a substantial stop state occurs. In this example, in a state where the suction pressure is Pin 3 or more and the subsequent pump is stopped, the flow of water to the subsequent pump becomes small, so the flow switch of the subsequent pump detects a low water amount state.

In this embodiment, when the suction pressure rises and the pump is stopped, the frequency command value to the pump that is operating at a variable speed is set so that the parallel operation is canceled and the subsequent pump is not disconnected and stopped. When 0 Hz, or when the suction pressure is PA or higher, or when HzB (frequency at which the cutoff pressure at that time is equal to or higher than the minimum required pressure PB of the water supply system) is 0, disconnection Control that no operation is performed is performed. That is, in this embodiment, as a condition for stopping the disconnection of the pump, in addition to the fact that the pump operating at variable speed is in a low water volume state, the frequency command to the pump is greater than 0 Hz, or the suction pressure Is not more than PA or HzB> 0 Hz.
With this control, in the present embodiment, the inflow pressure is Pin 4 and both the first and second pumps are stopped at the frequency command of 0 Hz, but the parallel operation is not released. When the suction pressure decreases from this point and becomes less than Pmax, HzMax becomes greater than 0 Hz. Therefore, the starting pump that is operated as a fixed speed pump is first restarted, and when the suction pressure is further decreased and becomes smaller than PA, the speed change operation is performed. The later pump will also restart.

  If parallel operation has been canceled as in the prior art, the pump will not restart until the suction pressure becomes lower than PA, but in this embodiment, the previous pump that was operated as a fixed speed pump before that is restarted. Since it has started, the amount of demand water is large, and stable water supply with suppressed pressure fluctuation is possible even when the suction pressure suddenly drops below PA. In this way, when the pump stops due to an increase in suction pressure during parallel operation, there is a difference in the stop conditions between the pump during variable speed operation and the pump during fixed speed operation. When the pump is restarted due to a decrease in the suction pressure, the fixed speed pump is started in advance before the discharge pressure falls below the target pressure even when the pump is restarted, enabling stable water supply with reduced pressure fluctuations. .

[Second Embodiment]
In the first embodiment described above, control is performed so that the frequency command value to the pump is reduced to 0 Hz when the suction pressure is increased, and the pump is in a substantially stopped state. However, the suction pressure has reached a predetermined value or more. Control to stop the pump may be performed depending on conditions.
Referring to FIG. 5, when the suction pressure exceeds a predetermined value equal to or higher than PA, which is the maximum target pressure of the water supply system, control is performed to stop the driving pump. If all the pumps are stopped in a state where they are being operated, a plurality of pumps must be restarted when the suction pressure suddenly decreases, and therefore pressure fluctuations are likely to occur.
In the present embodiment, a first pressure set value for stopping a pump that is operating at a variable speed and a second pressure set value for stopping a pump that is operating as a fixed speed pump are set. As described above, the first pressure set value is a predetermined value that is equal to or greater than PA, and the second pressure set value is higher than the first pressure set value. In FIG. A pressure value of is desirable.

When the suction pressure increases during the parallel operation of the pumps and becomes equal to or higher than the first pressure set value, the control device 15 stops the subsequent pump that is operating at a speed change, but the first pump that is operating as a fixed speed pump is stopped. Continue driving. When the suction pressure decreases and the discharge pressure falls below the target pressure, the subsequent pump is restarted. However, when the suction pressure further increases and exceeds the second pressure set value, the preceding pump is also stopped. When all the pumps are stopped, if the suction pressure falls below the second pressure set value, the first pump is restarted.If the discharge pressure falls below the target pressure, the second pump is restarted in the shift operation. The
Also in this embodiment, when the pump stops due to an increase in suction pressure during parallel operation, the pump under variable speed operation is given a difference in the stop conditions between the pump during variable speed operation and the pump during fixed speed operation. When the pump restarts due to a decrease in suction pressure, the fixed speed pump is started in advance before the discharge pressure falls below the target pressure, enabling stable water supply with reduced pressure fluctuations. Become.

It is a figure which shows the prior art example of the water supply apparatus which supplies water to a water supply end. It is a QH diagram at the time of performing the estimated terminal pressure constant control of the water supply apparatus which supplies water to a water supply end. It is a schematic block diagram of the direct connection type water supply apparatus which concerns on 1st Embodiment of this invention. It is a flowchart of the presumed terminal pressure fixed control of the water supply apparatus which supplies water to a water supply end. It is a graph showing the relationship between the operating frequency of a pump and the cutoff pressure at that time in control when suction pressure fluctuates.

Explanation of symbols

1 Motor pump 2 Inverter (frequency converter)
3 Pressure tank 4 Discharge pressure sensor 6 Flow switch (flow rate detection means)
7, 14 Check valve 8 Suction side piping 9 Water main pipe 10 Suction side pressure sensor 11 Backflow prevention device 12 Bypass pipe 13 Discharge side piping 15 Control device

Claims (6)

A plurality of pumps connected to the water main, a plurality of frequency converters that respectively shift the pumps, a discharge side pressure sensor, a suction side pressure sensor, and a control device that controls these devices, A directly connected water supply device that operates a plurality of pumps in parallel,
The control device performs parallel operation between a speed change pump that is speed-changed according to a pressure detected by the discharge-side pressure sensor and a fixed speed pump that is operated at a predetermined speed, and the suction pressure is reduced to the speed change pump. When the frequency command value is not 0 Hz and the speed change pump is in a low water amount state, the speed change pump is disconnected and stopped. A plurality of pumps connected to the water main, a plurality of frequency converters that respectively shift the pumps, a discharge side pressure sensor, a suction side pressure sensor, and a control device that controls these devices, A directly connected water supply device that operates a plurality of pumps in parallel,
The control device performs a parallel operation with a speed change pump that is operated in accordance with a pressure detected by the discharge side pressure sensor and a fixed speed pump that is operated at a predetermined speed, and the pump is driven by an increase in suction pressure during the parallel operation. When the engine is stopped, the transmission pump is stopped first with a difference in the stop conditions between the transmission pump and the fixed speed pump, and the transmission pump is restarted when the pump is restarted due to a decrease in suction pressure. A direct-coupled water supply apparatus, wherein the fixed speed pump is restarted in advance before starting.   The control device has a first pressure set value and a second pressure set value higher than the first pressure set value, and the detected pressure of the suction side pressure sensor during the parallel operation is the first pressure set value. When the pressure setting value is exceeded, the variable speed pump is stopped, and when the pressure setting value exceeds the second pressure setting value, the fixed speed pump is stopped, and the suction pressure is lowered and the detected pressure of the suction side pressure sensor becomes the second pressure. The direct-coupled water supply apparatus according to claim 2, wherein the fixed-speed pump is restarted when the pressure setting value of the fixed speed pump falls below. A plurality of pumps connected to the water main, a plurality of frequency converters that respectively shift the pumps, a discharge side pressure sensor, a suction side pressure sensor, and a control device that controls these devices, A directly connected water supply device that operates a plurality of pumps in parallel,
The control device performs a parallel operation with a speed change pump operated in accordance with a detection pressure of the discharge side pressure sensor and a fixed speed pump operated at a predetermined speed, and the suction pressure increases during the parallel operation due to an increase in the suction pressure. When restarting the pump due to a decrease in suction pressure after stopping the variable speed pump and the fixed speed pump, the fixed speed pump is restarted in advance before restarting the variable speed pump. Directly connected water supply system. The direct connection type water supply apparatus according to any one of claims 1 to 4, wherein the fixed speed pump is operated at a speed set in accordance with a pressure detected by the suction side pressure sensor. The control device sets the speed of the fixed speed pump that is set according to the pressure detected by the suction side pressure sensor so that the cutoff pressure at the speed is constant regardless of the fluctuation of the suction pressure. The directly connected water supply device according to claim 5, wherein

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