JPH0112960B2 - - Google Patents

Description

Detailed Description of the Invention The present invention utilizes a so-called clearance control method that changes characteristics by changing the gap between the open ends of the blades of an open impeller, so that even when the flow rate changes from maximum to minimum (0), , relates to the structure of a centrifugal pump in which the initially set discharge pressure is kept constant.

Conventionally, it has been common to use both rotational speed control and constant discharge pressure control, but this is expensive and has limited applications. As a countermeasure for this, a main shaft with a fixed impeller is supported so as to be slidable in the axial direction, and the main shaft is connected to a piston of a servo cylinder. ) The discharge pressure is introduced directly or through a throttle into the variable pressure chamber, and the constant pressure is introduced into the constant pressure chamber on the opposite side. It is also possible to make use of this characteristic) so that when the discharge pressure rises above the set pressure, the balance is broken and the gap in front of the vanes increases, and conversely, when the discharge pressure falls below the set pressure, the above gap decreases. However, since the purpose is to keep the discharge pressure constant, the discharge pressure does not originally fluctuate much more than the set pressure. Therefore, if the differential pressure is used as the power source for the servo piston, other power sources cannot be used. Although there is an advantage in not requiring it, the power is insufficient, and especially when shifting the impeller in the direction of reducing the gap in front of the blades, the impeller does not reach the required position, resulting in lower performance and lower discharge pressure than the required value. A problem arises.

The present invention detects the difference between the desired discharge pressure and the discharge pressure at each discharge amount during operation, and uses a hydraulic balance promoting mechanism consisting of a solenoid valve operated by a pressure switch to adjust the pressure between the variable pressure chamber and the constant pressure chamber. In other words, as the discharge pressure increases, the pressure in the variable pressure chamber increases and the gap in front of the blade increases. Also, if the discharge pressure decreases, the pressure in the variable pressure chamber will be lowered and the gap in front of the blades will be reduced. The invention will now be described with reference to the drawings.

The main shaft 1 in Fig. 1 is supported by a pump casing 4 at its front and rear ends (left and right in the figure) by bearings 2 and 3, and between them are first and second stage impellers that face forward (to the left in the figure) and are open. Wheels 5 and 6 are fixed, and a concentric motor (not shown) is connected to a portion protruding forward from the pump casing 4. The other end of the main shaft 1 is connected to a diaphragm 9 in a servo cylinder 8 via a joint 7 that can transmit only axial force. The cylinder 8 is fixed to the pump casing 4. 11 and 12 are vanes, 13 and 14 are fitted volute casings, 15 and 16 are suction ports of each impeller, 17 is a partition wall, 18 is a return vane, and the partition wall 17 is a part of the pump casing 4. It is provided in the volute casing type intermediate casing 20 that constitutes the structure. 19 is a discharge port.

The impellers 5 and 6 have an annular portion 77 and a balancing hole 78 on their rear surfaces in order to balance the front and rear thrusts.
In addition, the impellers 5 and 6, together with the main shaft 1 and bearings 2 and 3,
The impellers 5 and 6 can be slid rearward from the illustrated state where the gap a in front of each impeller is the smallest. That is, the front internal bearing 2 is connected to the external bearing 8 via the sleeve metal 82.
2, the external bearing 83 is fixed to the pump case 4, and the external bearing 83 is supported by the sleeve metal 8.
2 and a locking pin 84 for the internal bearing 2 are provided. Similarly, the rear internal bearing 3 is connected to the sleeve metal 92 by the external bearing 93 fixed to the pump case 4.
The internal bearing 3 is supported via the rotation stopper pin 9.
4 is provided. Reference numerals 85 and 95 are lubricating oil fill ports.

To explain the internal bearing 3, the internal bearing 3 has a cup-shaped joint main body 71 fitted from the rear onto the outer ring of a ball bearing 96 and fixed with a lid 97. By screwing together the screw provided at the front end of the portion 35, the joint 7 capable of transmitting only axial force as described above is constructed.

Pipes 27 and 29 are connected to the discharge port 19 and the low pressure portion of the pump (for example, the suction port 15), respectively.
Among the chambers 39 and 40 in the cylinder 8 separated by the diaphragm 9, the front variable pressure chamber 39 is connected to the pipe 4.
9. Discharge pressure piping 2 via first electrical control valve 59
7, and is also connected to the suction pressure pipe 29 via the pipe 50 and the second electric control valve 150. A pressure switch 55 or a combination of a pressure detector and an electric controller is connected to the discharge pressure pipe 27 via a pipe 53. The pressure switch 55 is electrically connected to the two electric control valves 59 and 150, and when the upper limit H ₃ (Fig. 2) of the discharge pressure is detected, the pressure switch 55 opens the valve 59 and closes the valve 150, thereby controlling the discharge pressure. When the lower pressure limit H ₂ is detected, valve 59 is closed and valve 150 is opened.

The cylinder 8 is formed by joining two cup-shaped members facing each other with bolts (not shown), and the outer peripheral edge of the diaphragm 9 is clamped by the joint portion 8a (outward flange).
A spring receiver 38 is arranged on the rear surface of the diaphragm 9 (the surface on the constant pressure chamber 40 side). The spring receiver 38 and the diaphragm 9 are screwed together with a nut 42 by passing a small diameter threaded portion at the rear end of the shaft portion 35 through a central hole and onto a washer 44 fitted to the front end of the screw. Spring receiver 38
A compression coil spring 41 is arranged between the rear wall of the cylinder 8 and the rear wall of the cylinder 8, and the spring 41 maintains the discharge setting pressure.
A constant pressure corresponding to H ₁ (Figure 2) is applied to the diaphragm 9. That is, among the discharge pressures when the gap a between the impellers 5 and 6 is at its minimum (when the pump performance is at its highest, as shown in S ₁ in Fig. 2), the pressure H ₁ (corresponding to the desired maximum water flow point Q _{n )} When the desired discharge pressure (i.e., discharge set pressure) is introduced into the variable pressure chamber 39, the diaphragm 9 (front position of the impellers 5 and 6)
stands still. The spring 41 is much longer than the amount of movement of the impellers 5 and 6, and the rate of expansion and contraction of the spring 17 due to the movement of the impellers 5 and 6 (diaphragm 9) is small, so the spring 17 applies almost constant pressure to the diaphragm 9. In addition to The upper limit pressure H ₃ and lower limit pressure H ₂ detected by the pressure switch 55 are distributed above and below the set pressure H ₁ .

If the gap a between the impellers is relatively large during pump operation, the pump performance will be low as shown in S ₄ in Figure 2, and when the water consumption is Q ₁ (operating point B), the discharge pressure will be H ₁
becomes. Due to the characteristic of general pumps that the discharge pressure decreases as the amount of water increases, when the amount of water used increases to _Q2 , the pressure decreases to the lower limit pressure _H2 (operating point C), and the pressure switch 55 detects this pressure decrease. to open valve 150 and close valve 59. As a result, the pressure in the variable pressure chamber 39 decreases, the diaphragm 9 moves forward, and the gap a decreases. As a result, the performance increases from S ₄ to S ₃ and the discharge pressure increases (operating point D). Valve 150 remains open, the performance increases further (S ₂ ), and the pressure reaches the upper pressure limit H ₃ . Pressure switch 55 detects this and closes valve 150.
is closed and valve 59 is opened. As a result, the variable pressure chamber 39
A discharge pressure H ₃ is introduced at. Pressure in variable pressure chamber
Since H ₃ exceeds the pressure H ₁ exerted by the spring 41, the diaphragm 9 moves rearward and the gap a increases. As the gap a increases, the pump performance decreases (S _2.5 ), and when the discharge pressure decreases to the set pressure H ₁ , the diaphragm 9 becomes balanced, the front and rear positions of the impellers 5 and 6 become stationary, and the pump performance S _2.5 and water flow Q _2. Operated at the operating point.

When the amount of water used decreases at this operating point,
The discharge pressure tries to rise along the performance curve _S2.5 , but as the discharge pressure rises, the pressure inside the variable pressure chamber 39 also rises, which causes the diaphragm 9 to close the gap a.
As a result, the discharge pressure is prevented from increasing, and the discharge pressure is maintained at the set value _H1 even if the water volume decreases.

Also, when the amount of water used increases at the operating point, the discharge pressure starts to decrease, but in that case, the variable pressure chamber 39
Even if the pressure decreases, during actual use, the diaphragm 9 does not move by the required amount due to insufficient force, and the pressure decreases to the lower limit _H2 . This pressure drop causes the pressure switch 55 to operate and open the valve 150.
9 is closed and the corrective action described above is applied to reach the desired pressure H ₁ .

In addition, when the water volume changes, the discharge pressure is set as the final setting.
It fluctuates between the upper limit H ₃ and the lower limit H ₂ before settling on H ₁ , but the difference between the upper limit H ₃ and the lower limit H ₂ is determined by the pressure switch 55.
If a micro switch or the like is used as the pressure switch 55, the difference can be reduced to 0.5 m or less, in which case the fluctuation difference H ₃ −
H ₂ is extremely small, on the order of 1%, even compared to the lowest water supply pump pressure of 30 m, so it is not a problem.

As explained above, according to the present invention, the normal 1
A constant discharge pressure pump can be obtained simply and inexpensively by slightly changing the structure of a stage or multistage centrifugal pump. Furthermore, since only the pressure in the variable pressure chamber 39 is controlled by one pressure switch 55, the structure of the hydraulic balance promotion mechanism is also simple. Furthermore, in the present invention, the variable pressure chamber 39 on the impeller opening side of the diaphragm 9 is connected to the discharge port 1 via the first electrical control valve 59.
9 and is connected to the suction port 15 via a second electric control valve 150, and is connected to the constant pressure side of the diaphragm 9 facing the constant pressure chamber 40 on the opposite side of the variable pressure chamber 39 to provide a constant pressure corresponding to a desired discharge pressure. A discharge pressure switch 55 is provided and connected to the first and second control valves, and when the discharge pressure reaches the upper limit, the first control valve 59 is opened and the second control valve 150 is closed, and the discharge pressure reaches the lower limit. When the discharge pressure reaches the lower limit, the first control valve 59 is closed and the second control valve 150 is opened.
The pressure is lowered to a pressure of
By increasing the thrust force pushing toward the left side in the figure, the front gap a can be quickly reduced. That is, compared to the conventional method, which simply continuously supplies discharge pressure to the variable pressure chamber 39 from the discharge port 19 and utilizes the pressure increase characteristic of the centrifugal pump (the characteristic that the pressure gradually increases from a large flow rate to a small flow rate). , when the discharge pressure falls below the set pressure, the pressure inside the variable pressure chamber 39 can be actively lowered to the pressure inside the suction port 15, and the problem of insufficient force to reduce the front clearance a is reliably prevented. The blades 11 and 12 quickly approach the partition wall 17 side to the required position. Therefore, there is an advantage that constant discharge pressure control can be performed with high precision. Moreover, according to the present invention, since the diaphragm 9 is directly connected to the main shaft 1, there is an advantage that the gap a in front of the blade can be controlled reliably.

Note that the following modifications are possible in the present invention.

(1) Instead of the electric control valve 150, a manual throttle valve 152 as shown in FIG. 3 may be used. Valve 1
When valve 152 opens, the discharge pressure (pump performance) increases as in the embodiment shown in FIG.
The rising speed (control response speed) can be adjusted by adjusting the degree of restriction. Note that in FIG. 3, the same reference numerals as in FIG. 1 indicate corresponding parts (the same applies hereinafter).

(2) A timer may be connected to the valve 150 so that the opening time of the valve 150 and/or the interval from "open" to "open" can be adjusted. In that case, the control response speed can be adjusted. Note that a timer can also be connected to the valve 59.

(3) It is also possible to adopt an oil or pneumatic control method to control the valves 59 and 150.

(4) It is also possible to replace the valves 59 and 150 with one three-way valve.

(5) The upper limit pressure _H3 can also be made to match the set pressure _H1 . In that case, when the discharge pressure rises to the set pressure _H1 , the valve 59 opens, and the same process as described above occurs when the discharge pressure once reaches the upper limit _H3 from the lower limit _H2 , and then reaches the set pressure _H1 . This prevents the pressure from rising even if it attempts to rise thereafter.

(6) One pressure switch 55 can be replaced with a combination of a pressure switch that detects the upper limit pressure _H3 and a pressure switch that detects the lower limit pressure _H2 . In that case, the pressure difference H ₃ −H ₂ can be set small.

(7) It is also possible to fill the cylinder 8 with hydraulic oil and separate it from the pumped liquid with another diaphragm or the like so that only the pressure is transmitted.

(8) As shown in FIG. 4, the bearing 3a and the joint 7a can be provided separately. 71a is a cup-shaped joint body fixed to the end of the main shaft 1, the outer ring 32 of the sealed ball bearing 31 is fitted inside and fixed with a lid 33, the shaft part 35 of the diaphragm 9 is fitted into the inner ring 34, and the nut is tightened. It is fixed at 36.
37 is a seal, 43 is a pressure inlet, and 45 is an outlet.

(9) Instead of the joint 7a shown in FIG. 4, the joint shown in FIG. 5 may be used. In the joint of FIG. 5, the inner ring 34 rotates and the outer ring 32 remains stationary. 6
7 and 68 are protrusions and grooves for preventing rotation, both of which engage with each other, and the protrusion 67 is fixed to the cylinder 8.

(10) In Fig. 1, the total thrust of the impeller is mostly balanced by the balancing hole 78, but instead of the balancing hole 78, a balance piston 66 can be used as shown in Fig. 6. You can also,
As shown in FIG. 7, an annular disk 22 is brought into contact with the outer periphery of the balance disk 21, a chamber B is formed on the front side of the disk 22, and the chamber B is connected through a passage 25 having a throttle valve (not shown). It is also possible to employ a mechanism in which the disk 22 slides following the balance disk 21 by connecting it to the discharge port 19. In the thrust balancing mechanism shown in FIGS. 6 and 7, the sizes of the balance piston 66, balance disk 21, and disc 22 are determined so as to balance the partial amount of thrust, and the remaining parts are held by the diaphragm 9. You can also do it.

(11) The cylinder 8 may be attached to the pump casing 4 parallel to the main shaft 1, and a fork rigidly fixed to the diaphragm 9 may be engaged with an annular groove provided on the main shaft 1. In that case, the overall length of the pump is reduced.

(12) When inputting to the main shaft 1 via a chain, gear, etc., the cylinder 8 can also be arranged on the input shaft.

(13) At least one impeller open to the front may be provided, and the impeller may be located at any position (for example, at the front stage).

(14) The illustrated example shows an open impeller with the entire front side open, but it is also possible to partially open the impeller, and by reversing the position of the cylinder, the rear part of the impeller is open (the front part is closed). ) can also be used.

(15) The impeller outlet may be a volute case or a guide vane (75 in Figure 8).

(16) The present invention can also be applied to vertical pumps.

(17) Instead of the spring 41 in FIG. 1, the constant pressure chamber 40 is connected to the discharge port 19 via the piping 52 as shown in FIG. A constant pressure valve 51 is provided, and a throttle valve 4 is provided.
The constant pressure chamber 40 can also be connected to the suction port 15 via a piping 53 having a set pressure 62, or if the discharge pressure is not used, the constant pressure chamber 40 can be connected to a set pressure piping 62,
It can also be connected to an external pressure supply pipe 64 (for example, water supply) via the constant pressure setting adjustment mechanism 63.
As a method of introducing water pressure into the constant pressure chamber 40, the first method is as follows.
As shown in FIG.
It can also be connected to the suction pressure pipe 29 (low pressure section) via the valve 260 and the valve 27.
By appropriately adjusting 0, the pressure inside the constant pressure chamber 40 can be set to a predetermined value.

The present invention can also be applied as follows.

(1) It is also possible to replace the valves 59 and 150 in FIG. 1 with a manual throttle valve 48 and a safety valve 153 (spring type, weight type, etc.) as shown in FIG. When the discharge pressure (pressure in the variable pressure chamber 39) increases, the safety valve 153 opens, thereby reducing the pressure in the variable pressure chamber 39, so that the above objective can be achieved.

(2) As shown in Figure 12, the constant pressure chamber was completely abolished, and the variable pressure chamber
It is also possible to apply pressure only to point 9. That is, the solenoid valves 250, 300 provided between the variable pressure chamber 39, the discharge port 19, and the suction port 15 are operated as follows by a control mechanism consisting of a pressure detector A, a setting device B, a regulator C, and a command device D. let When the discharge pressure falls below the set pressure, the valve 300 opens, the gap between the impellers becomes smaller, and the discharge pressure increases. valve 25
0 remains closed until the discharge pressure reaches the upper limit, and at the moment the upper limit is reached, pressure is applied in the variable pressure chamber 39 to balance the diaphragm 9 against the slat. The area of the diaphragm 9 is determined so that this pressure is slightly lower than the set pressure. As a result, when the discharge pressure reaches the upper limit and the valve 250 opens and the discharge pressure is introduced into the variable pressure chamber 39, the diaphragm 9 overcomes the thrust of the pump and moves in the direction of increasing the blade gap and lowering the discharge pressure. . In the above operation, if the difference between the upper limit pressure and the lower limit pressure is kept small,
The discharge pressure remains constant.

(3) Variable pressure chamber 39 and constant pressure chamber 40 as shown in Figure 13
is connected to an oil/pneumatic pump 51 via a switching valve 50, the discharge pressure of the pump P is detected by a pressure detector A, and the detected pressure is compared with the set pressure of a setting device B by a comparator C. , by issuing a command from the command device D according to the difference between the two pressures, the variable pressure chamber 3
It is also conceivable to adjust the pressure difference between the impeller 9 and the constant pressure chamber 40, thereby adjusting the gap between the impellers.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional view of the present invention, Fig. 2 is a graph for explaining the operation, Figs. 3 to 8 are longitudinal sectional views showing other embodiments, and Figs. 9 to 13 are structures showing various application examples. This is a schematic diagram. 1... main shaft, 5, 6... open impeller,
7...Joint, 8...Cylinder, 9...Diaphragm, 39...Variable pressure chamber, 40...Constant pressure chamber, 55
...Pressure switch (balance promotion mechanism).

Claims (1)

[Claims] 1. In a single-stage or multi-stage centrifugal pump having at least one open impeller, the main shaft to which the impeller is fixed is supported slidably in the axial direction, and the main shaft is a cylinder whose interior is partitioned by a diaphragm perpendicular to the main shaft. is fixed to the pump casing opposite one end of the
The diaphragm and the main shaft are connected to move in the same direction through a joint that can transmit only axial force, and the variable pressure chamber on the side of the diaphragm in the impeller opening direction is connected to the discharge port via the first electrical control valve. and a constant pressure corresponding to the desired discharge pressure is applied to the constant pressure surface of the diaphragm facing the constant pressure chamber on the opposite side of the variable pressure chamber.
A discharge pressure switch is provided and connected to the first and second control valves, and when the discharge pressure reaches the upper limit, the first control valve is opened and the second control valve is closed, and when the discharge pressure reaches the lower limit, the first control valve 59 is closed. A constant discharge pressure pump characterized in that the second control valve 150 is closed and the second control valve 150 is opened.