JPH0112959B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention utilizes a so-called clearance control method that changes the characteristics by changing the gap between the open ends of the blades of an open impeller, even when the flow rate changes from maximum to minimum (O). , 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 has the problem of being expensive and limiting its uses. As a countermeasure for this, a main shaft with a fixed impeller is supported slidably in the axial direction, and the main shaft is connected to a piston of a servo cylinder. Discharge pressure is introduced directly into the variable pressure chamber or through a restriction, and constant pressure is introduced into the constant pressure chamber on the opposite side to achieve the pressure increase characteristic (the pressure gradually increases from high flow rate to low flow rate) of a centrifugal pump. It is conceivable that this could be used to break the balance and increase the gap in front of the blades when the discharge pressure rises above the set pressure, and conversely to reduce the gap when the discharge pressure falls below the set pressure. Since the purpose is to keep the discharge pressure constant, the discharge pressure does not normally fluctuate much more than the set pressure. Therefore, if this differential pressure is used as the power source for the servo piston, no other power source is required. Although there are advantages, there is a problem that 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. arise.

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 in FIG. 1 is supported by the pump casing 4 at its front and rear ends (left and right in the figure) by bearings 2 and 3,
Meanwhile, the first one opened facing forward (to the left in the figure),
The second stage impellers 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 piston 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.
3, the external bearing 83 is fixed to the pump case 4, and the sleeve metal 8 is attached to the external bearing 83.
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 stop 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 to 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 section of the pump (for example, the suction port 15), respectively.
Chamber 3 in cylinder 8 separated by piston 9
Among the variable pressure chambers 9 and 40, the front variable pressure chamber 39 is connected to the discharge pressure pipe 27 via a pipe 49 having an electric control valve 59, and to the suction pressure pipe 29 via a pipe 50 having an electric control valve 150. do. The rear constant pressure chamber 40 is connected to the discharge pressure piping 27 via a piping 52 having a constant pressure valve 51 with a constant pressure on the secondary side (constant pressure chamber 40 side), and to the suction pressure piping via a piping 53 having a throttle valve 47. Connect to 29. 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
When the upper limit H ₃ of the discharge pressure (Fig. 2) is detected,
The valve 59 is opened and the valve 150 is closed, and when the lower limit _H2 of the discharge pressure is detected, the valve 59 is closed and the valve 150 is opened. Note that when the discharge pressure is not used as a means for obtaining a constant pressure in the constant pressure chamber 40, the constant pressure chamber 40 is connected to an external pressure supply piping 64 (for example, water supply) via a set pressure piping 62 and a constant pressure setting adjustment mechanism 63.

Next, to explain the constant pressure setting, the impeller 5,
Pressure H1 corresponding to the desired maximum water flow point Qm (desired discharge pressure, i.e., discharge setting pressure) is introduced into the variable pressure chamber 39, and by balancing this, a constant pressure at which the impellers 5, 6 (piston 9) are stationary is introduced into the constant pressure chamber 40. Note that the upper limit pressure H ₃ and lower limit pressure H ₂ detected by the pressure switch 55 are distributed above and below this 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 inside the variable pressure chamber 39 decreases, and the piston 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 initially set pressure H ₁ in the constant pressure chamber 40, the piston 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 piston 9 is balanced and the impellers 10, 1
1 is stationary, and the pump is operated at performance S _2.5 , water volume Q ₂ , and operating point.

When the amount of water used decreases at this operating point,
The discharge pressure tries to rise along the performance curve S _2.5 , but as the discharge pressure rises, the pressure in the variable pressure chamber 39 also rises, which causes the piston 9 to move in a direction that increases the gap a (decreases performance). In order to
As a result, the discharge pressure is prevented from increasing, and the discharge pressure is maintained at the set value _H1 even if the amount of water 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 piston 9 does not move by the required amount due to insufficient force, and the pressure decreases to the lower limit _H2 . This pressure drop activates pressure switch 55 to open valve 150 and close valve 59, applying the corrective action described above to achieve the desired pressure.
Reach H ₁ .

Note that when the amount of water changes, the discharge pressure fluctuates between the upper limit H ₃ and the lower limit H ₂ before finally settling on the set value H ₁ , but the difference between the upper limit H ₃ and the lower limit H ₂ is determined by the pressure switch 5.
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, and in that case, the fluctuation difference H _3
-H2 is extremely small, on the order of 1%, even when compared to the lowest water 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.

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.

(5) 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.

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

(7) As shown in FIG. 4, the bearing 3a and the joint 7a may be provided separately. 71a is a cup-shaped joint body fixed to the end of the main shaft 1, the outer side 32 of the sealed ball bearing 31 is fitted inside and fixed with a lid 33, the shaft part 35 of the piston 9 is fitted into the inner ring 34, and the nut is tightened. It is fixed at 36. 3
7 and 38 are seals, 41 is a rotation stopper pin fixed to the cylinder end cover, and pin 41 is the piston 9.
It is slidably fitted into the hole 42 of. 43,
44 is a pressure introduction port, and 45 and 46 are the same outlets.

(8) In place of the joint 7a shown in FIG. 4, the joints shown in FIGS. 5 and 6 may be used. In the joint of FIG. 5, the inner ring 34 rotates and the outer ring 32 remains stationary. Reference numerals 67 and 68 are protrusions and grooves for preventing rotation, which engage with each other, and the protrusion 67 is fixed to the cylinder 8. FIG. 6 shows an example in which the transmission mechanism (coupling), piston 69, and cylinder 70 are integrated. 74 is a thrust collar fixed to the main shaft 1, 72 is a thrust receiver, and 73 is a compression coil spring. The thrust receiver 72 may be a thrust ball bearing or a combination of two angular contact ball bearings, but in that case a holding mechanism such as grease is required.

(8) 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. 7. Alternatively, as shown in FIG. 8, 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 provided with a throttle valve (not shown). It is also possible to adopt a mechanism in which the disk 22 slides following the balance disk 21 by being connected to the discharge port 19 via the passage 25. In addition, in the thrust balancing mechanism shown in FIGS. 7 and 8, the balance piston 66 and balance disc 2 are used to balance the partial amount of thrust.
1. The size of the disk 22 can be determined in advance, and the remaining portion can be held by the piston 9.

(9) The cylinder 8 may be attached to the pump casing 4 parallel to the main shaft 1, and a fork rigidly fixed to the piston 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.

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

(11) 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).

(12) The illustrated example shows an open impeller with the entire front side open, but it is also possible to partially open the impeller.If the position of the cylinder is reversed, the rear side of the impeller can be opened (the front side is closed). ) can also be used.

(13) The impeller outlet may be a volute case or a guide vane (75 in Figure 9).

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

(15) It is also possible to input from the rear of the pump and place a servo motor in the front. For example, the first
In Figure 6, the rear end of the main shaft portion 1a that protrudes rearward of the first-stage pump is fitted with a joint 1 that is slidable in the axial direction.
00 (only one part shown) is connected to a drive mechanism (not shown), and two ball bearings 101 and a sliding metal 102 are connected to the outer peripheral surface of the main shaft portion 1a.
A joint 7a and a cylinder 8a corresponding to the joint 7 and cylinder 8 in FIG. 1 are connected to the main shaft portion 1b which projects forward.

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) It is also possible to obtain a constant pressure _H1 by disposing a compression coil spring 130 between the rear surface of the piston 9 and the inner surface of the rear wall of the cylinder 8 as shown in FIG.

(3) It is also conceivable to use a diaphragm 9a instead of the piston 9 in FIG. 11 as shown in FIG. 12. 35a is a shaft, 131 is a nut, and 132 is a spring bearing plate.

(4) As shown in Figure 13, the constant pressure chamber 40 is connected to the manual throttle valve 26.
Discharge pressure piping 27 via piping 261 with 0
and the suction pressure pipe 29 (low pressure section) via a pipe 271 having a manual throttle valve 270.
It is also possible to connect to In that case, by appropriately adjusting the valves 260 and 270, the pressure in the constant pressure chamber 40 can be set to a predetermined value, and the pressure in the first and third
The constant pressure valve 51 shown in the figure can be eliminated.

(5) Variable pressure chamber 39 and constant pressure chamber 40 as shown in Fig. 14
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.

(6) As shown in Figure 15, the constant pressure chamber is 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 controlled by a control mechanism consisting of a pressure detector A, a setting device B, a regulator C, and a command device D as follows. Activate. 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 2
50 is closed until the discharge pressure reaches the upper limit,
At the moment when the upper limit is reached, a pressure sufficient to balance the piston 9 against the thrust is applied in the variable pressure chamber 39. The area of the piston 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 chamber 39, the piston 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 will be constant.

[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 9, and 16 are longitudinal sectional views showing other embodiments, and Figs. 10 to 15 are various application examples. FIG. 1...Main shaft, 5, 6...Open impeller, 7...Joint, 8...Cylinder, 9...
... Piston, 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, a main shaft to which an impeller is fixed is supported slidably in the axial direction, and a cylinder fitted with a piston is attached to the main shaft concentrically or parallel to the main shaft. The piston and the main shaft are connected to move in the same direction through a joint that is fixedly installed at one end and can transmit only axial force, and of the two chambers in the cylinder separated by the piston, the one on the side toward which the impeller opens is A discharge pressure is introduced into the variable pressure chamber, a constant pressure corresponding to the desired discharge pressure is introduced into the constant pressure chamber on the opposite side, and the difference between the desired discharge pressure and the discharge pressure at each discharge amount during operation is detected. A constant discharge pressure pump characterized by being equipped with a hydraulic balancing mechanism that increases and decreases the pressure only in the variable pressure chamber.